Commit Graph

1228 Commits

Author SHA1 Message Date
Patrick Steinhardt
080b068ffb refs/files: stop using the_repository in parse_loose_ref_contents()
We implicitly rely on `the_repository` in `parse_loose_ref_contents()`
by calling `parse_oid_hex()`. Convert the function to instead use
`parse_oid_hex_algop()` and have callers pass in the hash algorithm to
use.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-07-30 13:41:23 -07:00
Patrick Steinhardt
f777f4d884 refs: stop using the_repository
Convert "refs.c" to stop using `the_repository` in favor of the repo
that gets passed in via `struct ref_store`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-07-30 13:41:23 -07:00
Junio C Hamano
c89facd58e Merge branch 'ps/ref-storage-migration-fix'
Hotfix for a topic already in -rc.

* ps/ref-storage-migration-fix:
  refs: fix format migration on Cygwin
2024-07-23 16:54:34 -07:00
Patrick Steinhardt
09c817383f refs: fix format migration on Cygwin
It was reported that t1460-refs-migrate.sh fails when using Cygwin with
errors like the following:

    error: could not link file '.git/ref_migration.sr9pEF/reftable' to '.git/reftable': Permission denied

As some debugging surfaced, the root cause of this is that some files of
the newly-initialized ref store are still open when the target format is
the "reftable" format, and Cygwin refuses to rename open files.

Fix this issue by closing the new ref store before renaming its files
into place. This is a slight change in behaviour compared to before,
where we kept the new ref store open and then updated the repository's
ref store to point to it.

While we could re-open the new ref store after we have moved files
around, this is ultimately unnecessary. We know that the only user of
`repo_migrate_ref_storage_format()` is the git-refs(1) command, and it
won't access the ref store after it has been migrated anyway. So
reinitializing the ref store would be a waste of time. Regardless of
that it is still sensible to leave the repository in a consistent state.
But instead of reinitializing the ref store, we can simply unset the
repo's ref store altogether and let `get_main_ref_store()` lazily
initialize the new ref store as required.

Reported-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-07-23 08:58:03 -07:00
Junio C Hamano
7b472da915 Merge branch 'ps/use-the-repository'
A CPP macro USE_THE_REPOSITORY_VARIABLE is introduced to help
transition the codebase to rely less on the availability of the
singleton the_repository instance.

* ps/use-the-repository:
  hex: guard declarations with `USE_THE_REPOSITORY_VARIABLE`
  t/helper: remove dependency on `the_repository` in "proc-receive"
  t/helper: fix segfault in "oid-array" command without repository
  t/helper: use correct object hash in partial-clone helper
  compat/fsmonitor: fix socket path in networked SHA256 repos
  replace-object: use hash algorithm from passed-in repository
  protocol-caps: use hash algorithm from passed-in repository
  oidset: pass hash algorithm when parsing file
  http-fetch: don't crash when parsing packfile without a repo
  hash-ll: merge with "hash.h"
  refs: avoid include cycle with "repository.h"
  global: introduce `USE_THE_REPOSITORY_VARIABLE` macro
  hash: require hash algorithm in `empty_tree_oid_hex()`
  hash: require hash algorithm in `is_empty_{blob,tree}_oid()`
  hash: make `is_null_oid()` independent of `the_repository`
  hash: convert `oidcmp()` and `oideq()` to compare whole hash
  global: ensure that object IDs are always padded
  hash: require hash algorithm in `oidread()` and `oidclr()`
  hash: require hash algorithm in `hasheq()`, `hashcmp()` and `hashclr()`
  hash: drop (mostly) unused `is_empty_{blob,tree}_sha1()` functions
2024-07-02 09:59:00 -07:00
Junio C Hamano
5f14d20984 Merge branch 'kn/update-ref-symref'
"git update-ref --stdin" learned to handle transactional updates of
symbolic-refs.

* kn/update-ref-symref:
  update-ref: add support for 'symref-update' command
  reftable: pick either 'oid' or 'target' for new updates
  update-ref: add support for 'symref-create' command
  update-ref: add support for 'symref-delete' command
  update-ref: add support for 'symref-verify' command
  refs: specify error for regular refs with `old_target`
  refs: create and use `ref_update_expects_existing_old_ref()`
2024-06-20 15:45:12 -07:00
Junio C Hamano
4216329457 Merge branch 'ps/no-writable-strings'
Building with "-Werror -Wwrite-strings" is now supported.

* ps/no-writable-strings: (27 commits)
  config.mak.dev: enable `-Wwrite-strings` warning
  builtin/merge: always store allocated strings in `pull_twohead`
  builtin/rebase: always store allocated string in `options.strategy`
  builtin/rebase: do not assign default backend to non-constant field
  imap-send: fix leaking memory in `imap_server_conf`
  imap-send: drop global `imap_server_conf` variable
  mailmap: always store allocated strings in mailmap blob
  revision: always store allocated strings in output encoding
  remote-curl: avoid assigning string constant to non-const variable
  send-pack: always allocate receive status
  parse-options: cast long name for OPTION_ALIAS
  http: do not assign string constant to non-const field
  compat/win32: fix const-correctness with string constants
  pretty: add casts for decoration option pointers
  object-file: make `buf` parameter of `index_mem()` a constant
  object-file: mark cached object buffers as const
  ident: add casts for fallback name and GECOS
  entry: refactor how we remove items for delayed checkouts
  line-log: always allocate the output prefix
  line-log: stop assigning string constant to file parent buffer
  ...
2024-06-17 15:55:58 -07:00
Patrick Steinhardt
e7da938570 global: introduce USE_THE_REPOSITORY_VARIABLE macro
Use of the `the_repository` variable is deprecated nowadays, and we
slowly but steadily convert the codebase to not use it anymore. Instead,
callers should be passing down the repository to work on via parameters.

It is hard though to prove that a given code unit does not use this
variable anymore. The most trivial case, merely demonstrating that there
is no direct use of `the_repository`, is already a bit of a pain during
code reviews as the reviewer needs to manually verify claims made by the
patch author. The bigger problem though is that we have many interfaces
that implicitly rely on `the_repository`.

Introduce a new `USE_THE_REPOSITORY_VARIABLE` macro that allows code
units to opt into usage of `the_repository`. The intent of this macro is
to demonstrate that a certain code unit does not use this variable
anymore, and to keep it from new dependencies on it in future changes,
be it explicit or implicit

For now, the macro only guards `the_repository` itself as well as
`the_hash_algo`. There are many more known interfaces where we have an
implicit dependency on `the_repository`, but those are not guarded at
the current point in time. Over time though, we should start to add
guards as required (or even better, just remove them).

Define the macro as required in our code units. As expected, most of our
code still relies on the global variable. Nearly all of our builtins
rely on the variable as there is no way yet to pass `the_repository` to
their entry point. For now, declare the macro in "biultin.h" to keep the
required changes at least a little bit more contained.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-14 10:26:33 -07:00
Patrick Steinhardt
9da95bda74 hash: require hash algorithm in oidread() and oidclr()
Both `oidread()` and `oidclr()` use `the_repository` to derive the hash
function that shall be used. Require callers to pass in the hash
algorithm to get rid of this implicit dependency.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-14 10:26:32 -07:00
Patrick Steinhardt
b567004b4b global: improve const correctness when assigning string constants
We're about to enable `-Wwrite-strings`, which changes the type of
string constants to `const char[]`. Fix various sites where we assign
such constants to non-const variables.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-07 10:30:48 -07:00
Karthik Nayak
ed3272720e update-ref: add support for 'symref-create' command
Add 'symref-create' command to the '--stdin' mode 'git-update-ref' to
allow creation of symbolic refs in a transaction. The 'symref-create'
command takes in a <new-target>, which the created <ref> will point to.

Also, support the 'core.prefersymlinkrefs' config, wherein if the config
is set and the filesystem supports symlinks, we create the symbolic ref
as a symlink. We fallback to creating a regular symref if creating the
symlink is unsuccessful.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-07 10:25:45 -07:00
Karthik Nayak
2343720967 update-ref: add support for 'symref-delete' command
Add a new command 'symref-delete' to allow deletions of symbolic refs in
a transaction via the '--stdin' mode of the 'git-update-ref' command.
The 'symref-delete' command can, when given an <old-target>, delete the
provided <ref> only when it points to <old-target>.

This command is only compatible with the 'no-deref' mode because we
optionally want to check the 'old_target' of the ref being deleted.
De-referencing a symbolic ref would provide a regular ref and we already
have the 'delete' command for regular refs.

While users can also use 'git symbolic-ref -d' to delete symbolic refs,
the 'symref-delete' command in 'git-update-ref' allows users to do so
within a transaction, which promises atomicity of the operation and can
be batched with other commands.

When no 'old_target' is provided it can also delete regular refs,
similar to how the 'delete' command can delete symrefs when no 'old_oid'
is provided.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-07 10:25:44 -07:00
Karthik Nayak
1451ac734f update-ref: add support for 'symref-verify' command
The 'symref-verify' command allows users to verify if a provided <ref>
contains the provided <old-target> without changing the <ref>. If
<old-target> is not provided, the command will verify that the <ref>
doesn't exist.

The command allows users to verify symbolic refs within a transaction,
and this means users can perform a set of changes in a transaction only
when the verification holds good.

Since we're checking for symbolic refs, this command will only work with
the 'no-deref' mode. This is because any dereferenced symbolic ref will
point to an object and not a ref and the regular 'verify' command can be
used in such situations.

Add required tests for symref support in 'verify'. Since we're here,
also add reflog checks for the pre-existing 'verify' tests, there is no
divergence from behavior, but we never tested to ensure that reflog
wasn't affected by the 'verify' command.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-07 10:25:44 -07:00
Karthik Nayak
aba381c090 refs: create and use ref_update_expects_existing_old_ref()
The files and reftable backend, need to check if a ref must exist, so
that the required validation can be done. A ref must exist only when the
`old_oid` value of the update has been explicitly set and it is not the
`null_oid` value.

Since we also support symrefs now, we need to ensure that even when
`old_target` is set a ref must exist. While this was missed when we
added symref support in transactions, there are no active users of this
path. As we introduce the 'symref-verify' command in the upcoming
commits, it is important to fix this.

So let's export this to a function called
`ref_update_expects_existing_old_ref()` and expose it internally via
'refs-internal.h'.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-07 10:25:44 -07:00
Patrick Steinhardt
6d6a3a99c7 refs: implement logic to migrate between ref storage formats
With the introduction of the new "reftable" backend, users may want to
migrate repositories between the backends without having to recreate the
whole repository. Add the logic to do so.

The implementation is generic and works with arbitrary ref storage
formats so that a backend does not need to implement any migration
logic. It does have a few limitations though:

  - We do not migrate repositories with worktrees, because worktrees
    have separate ref storages. It makes the overall affair more complex
    if we have to migrate multiple storages at once.

  - We do not migrate reflogs, because we have no interfaces to write
    many reflog entries.

  - We do not lock the repository for concurrent access, and thus
    concurrent writes may end up with weird in-between states. There is
    no way to fully lock the "files" backend for writes due to its
    format, and thus we punt on this topic altogether and defer to the
    user to avoid those from happening.

In other words, this version is a minimum viable product for migrating a
repository's ref storage format. It works alright for bare repos, which
often have neither worktrees nor reflogs. But it will not work for many
other repositories without some preparations. These limitations are not
set into stone though, and ideally we will eventually address them over
time.

The logic is not yet used by anything, and thus there are no tests for
it. Those will be added in the next commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-06 09:04:33 -07:00
Patrick Steinhardt
64a6dd8ffc refs: implement removal of ref storages
We're about to introduce logic to migrate ref storages. One part of the
migration will be to delete the files that are part of the old ref
storage format. We don't yet have a way to delete such data generically
across ref backends though.

Implement a new `delete` callback and expose it via a new
`ref_storage_delete()` function.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-06 09:04:33 -07:00
Patrick Steinhardt
fbd1a693c7 refs: allow to skip creation of reflog entries
The ref backends do not have any way to disable the creation of reflog
entries. This will be required for upcoming ref format migration logic
so that we do not create any entries that didn't exist in the original
ref database.

Provide a new `REF_SKIP_CREATE_REFLOG` flag that allows the caller to
disable reflog entry creation.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-06 09:04:31 -07:00
Patrick Steinhardt
6e1683ace9 refs: pass storage format to ref_store_init() explicitly
We're about to introduce logic to migrate refs from one storage format
to another one. This will require us to initialize a ref store with a
different format than the one used by the passed-in repository.

Prepare for this by accepting the desired ref storage format as
parameter.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-06 09:04:31 -07:00
Patrick Steinhardt
318efb966b refs: convert ref storage format to an enum
The ref storage format is tracked as a simple unsigned integer, which
makes it harder than necessary to discover what that integer actually is
or where its values are defined.

Convert the ref storage format to instead be an enum.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-06-06 09:04:31 -07:00
Junio C Hamano
16a592f132 Merge branch 'ps/pseudo-ref-terminology'
Terminology to call various ref-like things are getting
straightened out.

* ps/pseudo-ref-terminology:
  refs: refuse to write pseudorefs
  ref-filter: properly distinuish pseudo and root refs
  refs: pseudorefs are no refs
  refs: classify HEAD as a root ref
  refs: do not check ref existence in `is_root_ref()`
  refs: rename `is_special_ref()` to `is_pseudo_ref()`
  refs: rename `is_pseudoref()` to `is_root_ref()`
  Documentation/glossary: define root refs as refs
  Documentation/glossary: clarify limitations of pseudorefs
  Documentation/glossary: redefine pseudorefs as special refs
2024-05-28 11:17:06 -07:00
Junio C Hamano
0ff6d23a0f Merge branch 'ps/pseudo-ref-terminology' into ps/ref-storage-migration
* ps/pseudo-ref-terminology:
  refs: refuse to write pseudorefs
  ref-filter: properly distinuish pseudo and root refs
  refs: pseudorefs are no refs
  refs: classify HEAD as a root ref
  refs: do not check ref existence in `is_root_ref()`
  refs: rename `is_special_ref()` to `is_pseudo_ref()`
  refs: rename `is_pseudoref()` to `is_root_ref()`
  Documentation/glossary: define root refs as refs
  Documentation/glossary: clarify limitations of pseudorefs
  Documentation/glossary: redefine pseudorefs as special refs
2024-05-23 09:14:32 -07:00
Junio C Hamano
e55f364398 Merge branch 'ps/refs-without-the-repository-updates' into ps/ref-storage-migration
* ps/refs-without-the-repository-updates:
  refs/packed: remove references to `the_hash_algo`
  refs/files: remove references to `the_hash_algo`
  refs/files: use correct repository
  refs: remove `dwim_log()`
  refs: drop `git_default_branch_name()`
  refs: pass repo when peeling objects
  refs: move object peeling into "object.c"
  refs: pass ref store when detecting dangling symrefs
  refs: convert iteration over replace refs to accept ref store
  refs: retrieve worktree ref stores via associated repository
  refs: refactor `resolve_gitlink_ref()` to accept a repository
  refs: pass repo when retrieving submodule ref store
  refs: track ref stores via strmap
  refs: implement releasing ref storages
  refs: rename `init_db` callback to avoid confusion
  refs: adjust names for `init` and `init_db` callbacks
2024-05-23 09:14:08 -07:00
Junio C Hamano
4beb7a3b06 Merge branch 'kn/ref-transaction-symref'
Updates to symbolic refs can now be made as a part of ref
transaction.

* kn/ref-transaction-symref:
  refs: remove `create_symref` and associated dead code
  refs: rename `refs_create_symref()` to `refs_update_symref()`
  refs: use transaction in `refs_create_symref()`
  refs: add support for transactional symref updates
  refs: move `original_update_refname` to 'refs.c'
  refs: support symrefs in 'reference-transaction' hook
  files-backend: extract out `create_symref_lock()`
  refs: accept symref values in `ref_transaction_update()`
2024-05-20 11:20:04 -07:00
Patrick Steinhardt
2bb444b196 refs: remove dwim_log()
Remove `dwim_log()` in favor of `repo_dwim_log()` so that we can get rid
of one more dependency on `the_repository`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:39 -07:00
Patrick Steinhardt
97abaab5f6 refs: drop git_default_branch_name()
The `git_default_branch_name()` function is a thin wrapper around
`repo_default_branch_name()` with two differences:

  - We implicitly rely on `the_repository`.

  - We cache the default branch name.

None of the callsites of `git_default_branch_name()` are hot code paths
though, so the caching of the branch name is not really required.

Refactor the callsites to use `repo_default_branch_name()` instead and
drop `git_default_branch_name()`, thus getting rid of one more case
where we rely on `the_repository`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:39 -07:00
Patrick Steinhardt
30aaff437f refs: pass repo when peeling objects
Both `peel_object()` and `peel_iterated_oid()` implicitly rely on
`the_repository` to look up objects. Despite the fact that we want to
get rid of `the_repository`, it also leads to some restrictions in our
ref iterators when trying to retrieve the peeled value for a repository
other than `the_repository`.

Refactor these functions such that both take a repository as argument
and remove the now-unnecessary restrictions.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:39 -07:00
Patrick Steinhardt
19c76e8235 refs: move object peeling into "object.c"
Peeling an object has nothing to do with refs, but we still have the
code in "refs.c". Move it over into "object.c", which is a more natural
place to put it.

Ideally, we'd also move `peel_iterated_oid()` over into "object.c". But
this function is tied to the refs interfaces because it uses a global
ref iterator variable to optimize peeling when the iterator already has
the peeled object ID readily available.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:39 -07:00
Patrick Steinhardt
330a2ae60b refs: pass ref store when detecting dangling symrefs
Both `warn_dangling_symref()` and `warn_dangling_symrefs()` derive the
ref store via `the_repository`. Adapt them to instead take in the ref
store as a parameter. While at it, rename the functions to have a `ref_`
prefix to align them with other functions that take a ref store.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:38 -07:00
Patrick Steinhardt
8378c9d27b refs: convert iteration over replace refs to accept ref store
The function `for_each_replace_ref()` is a bit of an oddball across the
refs interfaces as it accepts a pointer to the repository instead of a
pointer to the ref store. The only reason for us to accept a repository
is so that we can eventually pass it back to the callback function that
the caller has provided. This is somewhat arbitrary though, as callers
that need the repository can instead make it accessible via the callback
payload.

Refactor the function to instead accept the ref store and adjust callers
accordingly. This allows us to get rid of some of the boilerplate that
we had to carry to pass along the repository and brings us in line with
the other functions that iterate through refs.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:38 -07:00
Patrick Steinhardt
dc7fb4f72c refs: retrieve worktree ref stores via associated repository
Similar as with the preceding commit, the worktree ref stores are always
looked up via `the_repository`. Also, again, those ref stores are stored
in a global map.

Refactor the code so that worktrees have a pointer to their repository.
Like this, we can move the global map into `struct repository` and stop
using `the_repository`. With this change, we can now in theory look up
worktree ref stores for repositories other than `the_repository`. In
practice, the worktree code will need further changes to look up
arbitrary worktrees.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:38 -07:00
Patrick Steinhardt
e19488a60a refs: refactor resolve_gitlink_ref() to accept a repository
In `resolve_gitlink_ref()` we implicitly rely on `the_repository` to
look up the submodule ref store. Now that we can look up submodule ref
stores for arbitrary repositories we can improve this function to
instead accept a repository as parameter for which we want to resolve
the gitlink.

Do so and adjust callers accordingly.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:38 -07:00
Patrick Steinhardt
965f8991e5 refs: pass repo when retrieving submodule ref store
Looking up submodule ref stores has two deficiencies:

  - The initialized subrepo will be attributed to `the_repository`.

  - The submodule ref store will be tracked in a global map.

This makes it impossible to have submodule ref stores for a repository
other than `the_repository`.

Modify the function to accept the parent repository as parameter and
move the global map into `struct repository`. Like this it becomes
possible to look up submodule ref stores for arbitrary repositories.

Note that this also adds a new reference to `the_repository` in
`resolve_gitlink_ref()`, which is part of the refs interfaces. This will
get adjusted in the next patch.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:37 -07:00
Patrick Steinhardt
f1782d185b refs: track ref stores via strmap
The refs code has two global maps that track the submodule and worktree
ref stores. Even though both of these maps track values by strings, we
still use a `struct hashmap` instead of a `struct strmap`. This has the
benefit of saving us an allocation because we can combine key and value
in a single struct. But it does introduce significant complexity that is
completely unneeded.

Refactor the code to use `struct strmap`s instead to reduce complexity.
It's unlikely that this will have any real-world impact on performance
given that most repositories likely won't have all that many ref stores.
Furthermore, this refactoring allows us to de-globalize those maps and
move them into `struct repository` in a subsequent commit more easily.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:37 -07:00
Patrick Steinhardt
71c871b48d refs: implement releasing ref storages
Ref storages are typically only initialized once for `the_repository`
and then never released. Until now we got away with that without causing
memory leaks because `the_repository` stays reachable, and because the
ref backend is reachable via `the_repository` its memory basically never
leaks.

This is about to change though because of the upcoming migration logic,
which will create a secondary ref storage. In that case, we will either
have to release the old or new ref storage to avoid leaks.

Implement a new `release` callback and expose it via a new
`ref_storage_release()` function.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:37 -07:00
Patrick Steinhardt
ed93ea1602 refs: rename init_db callback to avoid confusion
Reference backends have two callbacks `init` and `init_db`. The
similarity of these two callbacks has repeatedly confused me whenever I
was looking at them, where I always had to look up which of them does
what.

Rename the `init_db` callback to `create_on_disk`, which should
hopefully be clearer.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-17 10:33:36 -07:00
Patrick Steinhardt
8e4f5c2dc2 refs: refuse to write pseudorefs
Pseudorefs are not stored in the ref database as by definition, they
carry additional metadata that essentially makes them not a ref. As
such, writing pseudorefs via the ref backend does not make any sense
whatsoever as the ref backend wouldn't know how exactly to store the
data.

Restrict writing pseudorefs via the ref backend.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt
f1701f279a ref-filter: properly distinuish pseudo and root refs
The ref-filter interfaces currently define root refs as either a
detached HEAD or a pseudo ref. Pseudo refs aren't root refs though, so
let's properly distinguish those ref types.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt
993d57eded refs: pseudorefs are no refs
The `is_root_ref()` function will happily clarify a pseudoref as a root
ref, even though pseudorefs are no refs. Next to being wrong, it also
leads to inconsistent behaviour across ref backends: while the "files"
backend accidentally knows to parse those pseudorefs and thus yields
them to the caller, the "reftable" backend won't ever see the pseudoref
at all because they are never stored in the "reftable" backend.

Fix this issue by filtering out pseudorefs in `is_root_ref()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt
31951c2248 refs: classify HEAD as a root ref
Root refs are those refs that live in the root of the ref hierarchy.
Our old and venerable "HEAD" reference falls into this category, but we
don't yet classify it as such in `is_root_ref()`.

Adapt the function to also treat "HEAD" as a root ref. This change is
safe to do for all current callers:

  - `ref_kind_from_refname()` already handles "HEAD" explicitly before
    calling `is_root_ref()`.

  - The "files" and "reftable" backends explicitly call both
    `is_root_ref()` and `is_headref()` together.

This also aligns behaviour or `is_root_ref()` and `is_headref()` such
that we stop checking for ref existence. This changes semantics for our
backends:

  - In the reftable backend we already know that the ref must exist
    because `is_headref()` is called as part of the ref iterator. The
    existence check is thus redundant, and the change is safe to do.

  - In the files backend we use it when populating root refs, where we
    would skip adding the "HEAD" file if it was not possible to resolve
    it. The new behaviour is to instead mark "HEAD" as broken, which
    will cause us to emit warnings in various places.

As there are no callers of `is_headref()` left afer the refactoring, we
can absorb it completely into `is_root_ref()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt
afcd067dad refs: do not check ref existence in is_root_ref()
Before this patch series, root refs except for "HEAD" and our special
refs were classified as pseudorefs. Furthermore, our terminology
clarified that pseudorefs must not be symbolic refs. This restriction
is enforced in `is_root_ref()`, which explicitly checks that a supposed
root ref resolves to an object ID without recursing.

This has been extremely confusing right from the start because (in old
terminology) a ref name may sometimes be a pseudoref and sometimes not
depending on whether it is a symbolic or regular ref. This behaviour
does not seem reasonable at all and I very much doubt that it results in
anything sane.

Last but not least, the current behaviour can actually lead to a
segfault when calling `is_root_ref()` with a reference that either does
not exist or that is a symbolic ref because we never initialized `oid`,
but then read it via `is_null_oid()`.

We have now changed terminology to clarify that pseudorefs are really
only "MERGE_HEAD" and "FETCH_HEAD", whereas all the other refs that live
in the root of the ref hierarchy are just plain refs. Thus, we do not
need to check whether the ref is symbolic or not. In fact, we can now
avoid looking up the ref completely as the name is sufficient for us to
figure out whether something would be a root ref or not.

This change of course changes semantics for our callers. As there are
only three of them we can assess each of them individually:

  - "ref-filter.c:ref_kind_from_refname()" uses it to classify refs.
    It's clear that the intent is to classify based on the ref name,
    only.

  - "refs/reftable_backend.c:reftable_ref_iterator_advance()" uses it to
    filter root refs. Again, using existence checks is pointless here as
    the iterator has just surfaced the ref, so we know it does exist.

  - "refs/files_backend.c:add_pseudoref_and_head_entries()" uses it to
    determine whether it should add a ref to the root directory of its
    iterator. This had the effect that we skipped over any files that
    are either a symbolic ref, or which are not a ref at all.

    The new behaviour is to include symbolic refs know, which aligns us
    with the adapted terminology. Furthermore, files which look like
    root refs but aren't are now mark those as "broken". As broken refs
    are not surfaced by our tooling, this should not lead to a change in
    user-visible behaviour, but may cause us to emit warnings. This
    feels like the right thing to do as we would otherwise just silently
    ignore corrupted root refs completely.

So in all cases the existence check was either superfluous, not in line
with the adapted terminology or masked potential issues. This commit
thus changes the behaviour as proposed and drops the existence check
altogether.

Add a test that verifies that this does not change user-visible
behaviour. Namely, we still don't want to show broken refs to the user
by default in git-for-each-ref(1). What this does allow though is for
internal callers to surface dangling root refs when they pass in the
`DO_FOR_EACH_INCLUDE_BROKEN` flag.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:52 -07:00
Patrick Steinhardt
32019a7a76 refs: rename is_special_ref() to is_pseudo_ref()
Rename `is_special_ref()` to `is_pseudo_ref()` to adapt to the newly
defined terminology in our gitglossary(7). Note that in the preceding
commit we have just renamed `is_pseudoref()` to `is_root_ref()`, where
there may be confusion for in-flight patch series that add new calls to
`is_pseudoref()`. In order to intentionally break such patch series we
have thus picked `is_pseudo_ref()` instead of `is_pseudoref()` as the
new name.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:51 -07:00
Patrick Steinhardt
f6936e62a5 refs: rename is_pseudoref() to is_root_ref()
Rename `is_pseudoref()` to `is_root_ref()` to adapt to the newly defined
terminology in our gitglossary(7).

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-15 07:30:51 -07:00
Patrick Steinhardt
c8f815c208 refs: remove functions without ref store
The preceding commit has rewritten all callers of ref-related functions
to use the equivalents that accept a `struct ref_store`. Consequently,
the respective variants without the ref store are now unused. Remove
them.

There are likely patch series in-flight that use the now-removed
functions. To help the authors, the old implementations have been added
to "refs.c" in an ifdef'd section as a reference for how to migrate each
of the respective callers.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 10:06:59 -07:00
Patrick Steinhardt
2e5c4758b7 cocci: apply rules to rewrite callers of "refs" interfaces
Apply the rules that rewrite callers of "refs" interfaces to explicitly
pass `struct ref_store`. The resulting patch has been applied with the
`--whitespace=fix` option.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 10:06:59 -07:00
Patrick Steinhardt
54876c6dfb refs: add exclude_patterns parameter to for_each_fullref_in()
The `for_each_fullref_in()` function is supposedly the ref-store-less
equivalent of `refs_for_each_fullref_in()`, but the latter has gained a
new parameter `exclude_patterns` over time. Bring these two functions
back in sync again by adding the parameter to the former function, as
well.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 10:06:59 -07:00
Patrick Steinhardt
39a9ef8fc4 refs: introduce missing functions that accept a struct ref_store
While most of the functions in "refs.h" have a variant that accepts a
`struct ref_store`, some don't. Callers of these functions are thus
forced to implicitly rely on `the_repository` to figure out the ref
store that is to be used.

Introduce those missing functions to address this shortcoming.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 10:06:58 -07:00
Karthik Nayak
f151dfe3c9 refs: rename refs_create_symref() to refs_update_symref()
The `refs_create_symref()` function is used to update/create a symref.
But it doesn't check the old target of the symref, if existing. It force
updates the symref. In this regard, the name `refs_create_symref()` is a
bit misleading. So let's rename it to `refs_update_symref()`. This is
akin to how 'git-update-ref(1)' also allows us to create apart from
update.

While we're here, rename the arguments in the function to clarify what
they actually signify and reduce confusion.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:50 -07:00
Karthik Nayak
300b38e46f refs: use transaction in refs_create_symref()
The `refs_create_symref()` function updates a symref to a given new
target. To do this, it uses a ref-backend specific function
`create_symref()`.

In the previous commits, we introduced symref support in transactions.
This means we can now use transactions to perform symref updates and
don't have to resort to `create_symref()`. Doing this allows us to
remove and cleanup `create_symref()`, which we will do in the following
commit.

Modify the expected error message for a test in
't/t0610-reftable-basics.sh', since the error is now thrown from
'refs.c'. This is because in transactional updates, F/D conflicts are
caught before we're in the reference backend.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:50 -07:00
Karthik Nayak
644daf7785 refs: add support for transactional symref updates
The reference backends currently support transactional reference
updates. While this is exposed to users via 'git-update-ref' and its
'--stdin' mode, it is also used internally within various commands.

However, we do not support transactional updates of symrefs. This commit
adds support for symrefs in both the 'files' and the 'reftable' backend.

Here, we add and use `ref_update_has_null_new_value()`, a helper
function which is used to check if there is a new_value in a reference
update. The new value could either be a symref target `new_target` or a
OID `new_oid`.

We also add another common function `ref_update_check_old_target` which
will be used to check if the update's old_target corresponds to a
reference's current target.

Now transactional updates (verify, create, delete, update) can be used
for:
- regular refs
- symbolic refs
- conversion of regular to symbolic refs and vice versa

This also allows us to expose this to users via new commands in
'git-update-ref' in the future.

Note that a dangling symref update does not record a new reflog entry,
which is unchanged before and after this commit.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:49 -07:00
Karthik Nayak
e9965ba477 refs: move original_update_refname to 'refs.c'
The files backend and the reftable backend implement
`original_update_refname` to obtain the original refname of the update.
Move it out to 'refs.c' and only expose it internally to the refs
library. This will be used in an upcoming commit to also introduce
another common functionality for the two backends.

We also rename the function to `ref_update_original_update_refname` to
keep it consistent with the upcoming other 'ref_update_*' functions
that'll be introduced.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:49 -07:00
Karthik Nayak
a8ae923f85 refs: support symrefs in 'reference-transaction' hook
The 'reference-transaction' hook runs whenever a reference update is
made to the system. In a previous commit, we added the `old_target` and
`new_target` fields to the `reference_transaction_update()`. In
following commits we'll also add the code to handle symref's in the
reference backends.

Support symrefs also in the 'reference-transaction' hook, by modifying
the current format:
    <old-oid> SP <new-oid> SP <ref-name> LF
to be be:
    <old-value> SP <new-value> SP <ref-name> LF
where for regular refs the output would not change and remain the same.
But when either 'old-value' or 'new-value' is a symref, we print the ref
as 'ref:<ref-target>'.

This does break backward compatibility, but the 'reference-transaction'
hook's documentation always stated that support for symbolic references
may be added in the future.

We do not add any tests in this commit since there is no git command
which activates this flow, in an upcoming commit, we'll start using
transaction based symref updates as the default, we'll add tests there
for the hook too.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:49 -07:00
Karthik Nayak
1bc4cc3fc4 refs: accept symref values in ref_transaction_update()
The function `ref_transaction_update()` obtains ref information and
flags to create a `ref_update` and add them to the transaction at hand.

To extend symref support in transactions, we need to also accept the
old and new ref targets and process it. This commit adds the required
parameters to the function and modifies all call sites.

The two parameters added are `new_target` and `old_target`. The
`new_target` is used to denote what the reference should point to when
the transaction is applied. Some functions allow this parameter to be
NULL, meaning that the reference is not changed.

The `old_target` denotes the value the reference must have before the
update. Some functions allow this parameter to be NULL, meaning that the
old value of the reference is not checked.

We also update the internal function `ref_transaction_add_update()`
similarly to take the two new parameters.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-07 08:51:49 -07:00
Junio C Hamano
d037212d97 Merge branch 'kn/for-all-refs'
"git for-each-ref" learned "--include-root-refs" option to show
even the stuff outside the 'refs/' hierarchy.

* kn/for-all-refs:
  for-each-ref: add new option to include root refs
  ref-filter: rename 'FILTER_REFS_ALL' to 'FILTER_REFS_REGULAR'
  refs: introduce `refs_for_each_include_root_refs()`
  refs: extract out `loose_fill_ref_dir_regular_file()`
  refs: introduce `is_pseudoref()` and `is_headref()`
2024-03-05 09:44:44 -08:00
Junio C Hamano
74522bbd98 Merge branch 'jk/reflog-special-cases-fix'
The logic to access reflog entries by date and number had ugly
corner cases at the boundaries, which have been cleaned up.

* jk/reflog-special-cases-fix:
  read_ref_at(): special-case ref@{0} for an empty reflog
  get_oid_basic(): special-case ref@{n} for oldest reflog entry
  Revert "refs: allow @{n} to work with n-sized reflog"
2024-03-05 09:44:42 -08:00
Jeff King
5edd126720 read_ref_at(): special-case ref@{0} for an empty reflog
The previous commit special-cased get_oid_basic()'s handling of ref@{n}
for a reflog with n entries. But its special case doesn't work for
ref@{0} in an empty reflog, because read_ref_at() dies when it notices
the empty reflog!

We can make this work by special-casing this in read_ref_at(). It's
somewhat gross, for two reasons:

  1. We have no reflog entry to describe in the "msg" out-parameter. So
     we have to leave it uninitialized or make something up.

  2. Likewise, we have no oid to put in the "oid" out-parameter. Leaving
     it untouched is actually the best thing here, as all of the callers
     will have initialized it with the current ref value via
     repo_dwim_log(). This is rather subtle, but it is how things worked
     in 6436a20284 (refs: allow @{n} to work with n-sized reflog,
     2021-01-07) before we reverted it.

The key difference from 6436a20284 here is that we'll return "1" to
indicate that we _didn't_ find the requested reflog entry. Coupled with
the special-casing in get_oid_basic() in the previous commit, that's
enough to make looking up ref@{0} work, and we can flip 6436a20284's
test back to expect_success.

It also means that the call in show-branch which segfaulted with
6436a20284 (and which is now tested in t3202) remains OK. The caller
notices that we could not find any reflog entry, and so it breaks out of
its loop, showing nothing. This is different from the current behavior
of producing an error, but it's just as reasonable (and is exactly what
we'd do if you asked it to walk starting at ref@{1} but there was only 1
entry).

Thus nobody should actually look at the reflog entry info we return. But
we'll still put in some fake values just to be on the safe side, since
this is such a subtle and confusing interface. Likewise, we'll document
what's going on in a comment above the function declaration. If this
were a function with a lot of callers, the footgun would probably not be
worth it. But it has only ever had two callers in its 18-year existence,
and it seems unlikely to grow more. So let's hold our noses and let
users enjoy the convenience of a simulated ref@{0}.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-26 10:05:35 -08:00
Jeff King
755e7465c9 get_oid_basic(): special-case ref@{n} for oldest reflog entry
The goal of 6436a20284 (refs: allow @{n} to work with n-sized reflog,
2021-01-07) was that if we have "n" entries in a reflog, we should still
be able to resolve ref@{n} by looking at the "old" value of the oldest
entry.

Commit 6436a20284 tried to put the logic into read_ref_at() by shifting
its idea of "n" by one. But we reverted that in the previous commit,
since it led to bugs in other callers which cared about the details of
the reflog entry we found. Instead, let's put the special case into the
caller that resolves @{n}, as it cares only about the oid.

read_ref_at() is even kind enough to return the "old" value from the
final reflog; it just returns "1" to signal to us that we ran off the
end of the reflog. But we can notice in the caller that we read just
enough records for that "old" value to be the one we're looking for, and
use it.

Note that read_ref_at() could notice this case, too, and just return 0.
But we don't want to do that, because the caller must be made aware that
we only found the oid, not an actual reflog entry (and the call sites in
show-branch do care about this).

There is one complication, though. When read_ref_at() hits a truncated
reflog, it will return the "old" value of the oldest entry only if it is
not the null oid. Otherwise, it actually returns the "new" value from
that entry! This bit of fudging is due to d1a4489a56 (avoid null SHA1 in
oldest reflog, 2008-07-08), where asking for "ref@{20.years.ago}" for a
ref created recently will produce the initial value as a convenience
(even though technically it did not exist 20 years ago).

But this convenience is only useful for time-based cutoffs. For
count-based cutoffs, get_oid_basic() has always simply complained about
going too far back:

  $ git rev-parse HEAD@{20}
  fatal: log for 'HEAD' only has 16 entries

and we should continue to do so, rather than returning a nonsense value
(there's even a test in t1508 already which covers this). So let's have
the d1a4489a56 code kick in only when doing timestamp-based cutoffs.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-26 10:05:32 -08:00
Jeff King
aa72e73a2e Revert "refs: allow @{n} to work with n-sized reflog"
This reverts commit 6436a20284.

The idea of that commit is that if read_ref_at() is counting back to the
Nth reflog but the reflog is short by one entry (e.g., because it was
pruned), we can find the oid of the missing entry by looking at the
"before" oid value of the entry that comes after it (whereas before, we
looked at the "after" value of each entry and complained that we
couldn't find the one from before the truncation).

This works fine for resolving the oid of ref@{n}, as it is used by
get_oid_basic(), which does not look at any other aspect of the reflog
we found (e.g., its timestamp or message). But there's another caller of
read_ref_at(): in show-branch we use it to walk over the reflog, and we
do care about the reflog entry. And so that commit broke "show-branch
--reflog"; it shows the reflog message for ref@{0} as ref@{1}, ref@{1}
as ref@{2}, and so on.

For example, in the new test in t3202 we produce:

  ! [branch@{0}] (0 seconds ago) commit: three
   ! [branch@{1}] (0 seconds ago) commit: three
    ! [branch@{2}] (60 seconds ago) commit: two
     ! [branch@{3}] (2 minutes ago) reset: moving to HEAD^

instead of the correct:

  ! [branch@{0}] (0 seconds ago) commit: three
   ! [branch@{1}] (60 seconds ago) commit: two
    ! [branch@{2}] (2 minutes ago) reset: moving to HEAD^
     ! [branch@{3}] (2 minutes ago) commit: one

But there's another bug, too: because it is looking at the "old" value
of the reflog after the one we're interested in, it has to special-case
ref@{0} (since there isn't anything after it). That's why it doesn't
show the offset bug in the output above. But this special-case code
fails to handle the situation where the reflog is empty or missing; it
returns success even though the reflog message out-parameter has been
left uninitialized. You can't trigger this through get_oid_basic(), but
"show-branch --reflog" will pretty reliably segfault as it tries to
access the garbage pointer.

Fixing the segfault would be pretty easy. But the off-by-one problem is
inherent in this approach. So let's start by reverting the commit to
give us a clean slate to work with.

This isn't a pure revert; all of the code changes are reverted, but for
the tests:

  1. We'll flip the cases in t1508 to expect_failure; making these work
     was the goal of 6436a2028, and we'll want to use them for our
     replacement approach.

  2. There's a test in t3202 for "show-branch --reflog", but it expects
     the broken output! It was added by f2463490c4 (show-branch: show
     reflog message, 2021-12-02) which was fixing another bug, and I
     think the author simply didn't notice that the second line showed
     the wrong reflog.

     Rather than fixing that test, let's replace it with one that is
     more thorough (while still covering the reflog message fix from
     that commit). We'll use a longer reflog, which lets us see more
     entries (thus making the "off by one" pattern much more clear). And
     we'll use a more recent timestamp for "now" so that our relative
     dates have more resolution. That lets us see that the reflog dates
     are correct (whereas when you are 4 years away, two entries that
     are 60 seconds apart will have the same "4 years ago" relative
     date). Because we're adjusting the repository state, I've moved
     this new test to the end of the script, leaving the other tests
     undisturbed.

     We'll also add a new test which covers the missing reflog case;
     previously it segfaulted, but now it reports the empty reflog).

Reported-by: Yasushi SHOJI <yasushi.shoji@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-26 10:05:28 -08:00
Karthik Nayak
d0f00c1ac1 refs: introduce refs_for_each_include_root_refs()
Introduce a new ref iteration flag `DO_FOR_EACH_INCLUDE_ROOT_REFS`,
which will be used to iterate over regular refs plus pseudorefs and
HEAD.

Refs which fall outside the `refs/` and aren't either pseudorefs or HEAD
are more of a grey area. This is because we don't block the users from
creating such refs but they are not officially supported.

Introduce `refs_for_each_include_root_refs()` which calls
`do_for_each_ref()` with this newly introduced flag.

In `refs/files-backend.c`, introduce a new function
`add_pseudoref_and_head_entries()` to add pseudorefs and HEAD to the
`ref_dir`. We then finally call `add_pseudoref_and_head_entries()`
whenever the `DO_FOR_EACH_INCLUDE_ROOT_REFS` flag is set. Any new ref
backend will also have to implement similar changes on its end.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-23 10:36:27 -08:00
Karthik Nayak
1eba2240f8 refs: introduce is_pseudoref() and is_headref()
Introduce two new functions `is_pseudoref()` and `is_headref()`. This
provides the necessary functionality for us to add pseudorefs and HEAD
to the loose ref cache in the files backend, allowing us to build
tooling to print these refs.

The `is_pseudoref()` function internally calls `is_pseudoref_syntax()`
but adds onto it by also checking to ensure that the pseudoref either
ends with a "_HEAD" suffix or matches a list of exceptions. After which
we also parse the contents of the pseudoref to ensure that it conforms
to the ref format.

We cannot directly add the new syntax checks to `is_pseudoref_syntax()`
because the function is also used by `is_current_worktree_ref()` and
making it stricter to match only known pseudorefs might have unintended
consequences due to files like 'BISECT_START' which isn't a pseudoref
but sometimes contains object ID.

Keeping this in mind, we leave `is_pseudoref_syntax()` as is and create
`is_pseudoref()` which is stricter. Ideally we'd want to move the new
syntax checks to `is_pseudoref_syntax()` but a prerequisite for this
would be to actually remove the exception list by converting those
pseudorefs to also contain a '_HEAD' suffix and perhaps move bisect
related files like 'BISECT_START' to a new directory similar to the
'rebase-merge' directory.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-23 10:36:27 -08:00
Patrick Steinhardt
31f898397b refs: drop unused params from the reflog iterator callback
The ref and reflog iterators share much of the same underlying code to
iterate over the corresponding entries. This results in some weird code
because the reflog iterator also exposes an object ID as well as a flag
to the callback function. Neither of these fields do refer to the reflog
though -- they refer to the corresponding ref with the same name. This
is quite misleading. In practice at least the object ID cannot really be
implemented in any other way as a reflog does not have a specific object
ID in the first place. This is further stressed by the fact that none of
the callbacks except for our test helper make use of these fields.

Split up the infrastucture so that ref and reflog iterators use separate
callback signatures. This allows us to drop the nonsensical fields from
the reflog iterator.

Note that internally, the backends still use the same shared infra to
iterate over both types. As the backends should never end up being
called directly anyway, this is not much of a problem and thus kept
as-is for simplicity's sake.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-21 09:58:06 -08:00
Patrick Steinhardt
5e01d83841 refs: always treat iterators as ordered
In the preceding commit we have converted the reflog iterator of the
"files" backend to be ordered, which was the only remaining ref iterator
that wasn't ordered. Refactor the ref iterator infrastructure so that we
always assume iterators to be ordered, thus simplifying the code.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-21 09:58:06 -08:00
Patrick Steinhardt
57db2a094d refs: introduce reftable backend
Due to scalability issues, Shawn Pearce has originally proposed a new
"reftable" format more than six years ago [1]. Initially, this new
format was implemented in JGit with promising results. Around two years
ago, we have then added the "reftable" library to the Git codebase via
a4bbd13be3 (Merge branch 'hn/reftable', 2021-12-15). With this we have
landed all the low-level code to read and write reftables. Notably
missing though was the integration of this low-level code into the Git
code base in the form of a new ref backend that ties all of this
together.

This gap is now finally closed by introducing a new "reftable" backend
into the Git codebase. This new backend promises to bring some notable
improvements to Git repositories:

  - It becomes possible to do truly atomic writes where either all refs
    are committed to disk or none are. This was not possible with the
    "files" backend because ref updates were split across multiple loose
    files.

  - The disk space required to store many refs is reduced, both compared
    to loose refs and packed-refs. This is enabled both by the reftable
    format being a binary format, which is more compact, and by prefix
    compression.

  - We can ignore filesystem-specific behaviour as ref names are not
    encoded via paths anymore. This means there is no need to handle
    case sensitivity on Windows systems or Unicode precomposition on
    macOS.

  - There is no need to rewrite the complete refdb anymore every time a
    ref is being deleted like it was the case for packed-refs. This
    means that ref deletions are now constant time instead of scaling
    linearly with the number of refs.

  - We can ignore file/directory conflicts so that it becomes possible
    to store both "refs/heads/foo" and "refs/heads/foo/bar".

  - Due to this property we can retain reflogs for deleted refs. We have
    previously been deleting reflogs together with their refs to avoid
    file/directory conflicts, which is not necessary anymore.

  - We can properly enumerate all refs. With the "files" backend it is
    not easily possible to distinguish between refs and non-refs because
    they may live side by side in the gitdir.

Not all of these improvements are realized with the current "reftable"
backend implementation. At this point, the new backend is supposed to be
a drop-in replacement for the "files" backend that is used by basically
all Git repositories nowadays. It strives for 1:1 compatibility, which
means that a user can expect the same behaviour regardless of whether
they use the "reftable" backend or the "files" backend for most of the
part.

Most notably, this means we artificially limit the capabilities of the
"reftable" backend to match the limits of the "files" backend. It is not
possible to create refs that would end up with file/directory conflicts,
we do not retain reflogs, we perform stricter-than-necessary checks.
This is done intentionally due to two main reasons:

  - It makes it significantly easier to land the "reftable" backend as
    tests behave the same. It would be tough to argue for each and every
    single test that doesn't pass with the "reftable" backend.

  - It ensures compatibility between repositories that use the "files"
    backend and repositories that use the "reftable" backend. Like this,
    hosters can migrate their repositories to use the "reftable" backend
    without causing issues for clients that use the "files" backend in
    their clones.

It is expected that these artificial limitations may eventually go away
in the long term.

Performance-wise things very much depend on the actual workload. The
following benchmarks compare the "files" and "reftable" backends in the
current version:

  - Creating N refs in separate transactions shows that the "files"
    backend is ~50% faster. This is not surprising given that creating a
    ref only requires us to create a single loose ref. The "reftable"
    backend will also perform auto compaction on updates. In real-world
    workloads we would likely also want to perform pack loose refs,
    which would likely change the picture.

        Benchmark 1: update-ref: create refs sequentially (refformat = files, refcount = 1)
          Time (mean ± σ):       2.1 ms ±   0.3 ms    [User: 0.6 ms, System: 1.7 ms]
          Range (min … max):     1.8 ms …   4.3 ms    133 runs

        Benchmark 2: update-ref: create refs sequentially (refformat = reftable, refcount = 1)
          Time (mean ± σ):       2.7 ms ±   0.1 ms    [User: 0.6 ms, System: 2.2 ms]
          Range (min … max):     2.4 ms …   2.9 ms    132 runs

        Benchmark 3: update-ref: create refs sequentially (refformat = files, refcount = 1000)
          Time (mean ± σ):      1.975 s ±  0.006 s    [User: 0.437 s, System: 1.535 s]
          Range (min … max):    1.969 s …  1.980 s    3 runs

        Benchmark 4: update-ref: create refs sequentially (refformat = reftable, refcount = 1000)
          Time (mean ± σ):      2.611 s ±  0.013 s    [User: 0.782 s, System: 1.825 s]
          Range (min … max):    2.597 s …  2.622 s    3 runs

        Benchmark 5: update-ref: create refs sequentially (refformat = files, refcount = 100000)
          Time (mean ± σ):     198.442 s ±  0.241 s    [User: 43.051 s, System: 155.250 s]
          Range (min … max):   198.189 s … 198.670 s    3 runs

        Benchmark 6: update-ref: create refs sequentially (refformat = reftable, refcount = 100000)
          Time (mean ± σ):     294.509 s ±  4.269 s    [User: 104.046 s, System: 190.326 s]
          Range (min … max):   290.223 s … 298.761 s    3 runs

  - Creating N refs in a single transaction shows that the "files"
    backend is significantly slower once we start to write many refs.
    The "reftable" backend only needs to update two files, whereas the
    "files" backend needs to write one file per ref.

        Benchmark 1: update-ref: create many refs (refformat = files, refcount = 1)
          Time (mean ± σ):       1.9 ms ±   0.1 ms    [User: 0.4 ms, System: 1.4 ms]
          Range (min … max):     1.8 ms …   2.6 ms    151 runs

        Benchmark 2: update-ref: create many refs (refformat = reftable, refcount = 1)
          Time (mean ± σ):       2.5 ms ±   0.1 ms    [User: 0.7 ms, System: 1.7 ms]
          Range (min … max):     2.4 ms …   3.4 ms    148 runs

        Benchmark 3: update-ref: create many refs (refformat = files, refcount = 1000)
          Time (mean ± σ):     152.5 ms ±   5.2 ms    [User: 19.1 ms, System: 133.1 ms]
          Range (min … max):   148.5 ms … 167.8 ms    15 runs

        Benchmark 4: update-ref: create many refs (refformat = reftable, refcount = 1000)
          Time (mean ± σ):      58.0 ms ±   2.5 ms    [User: 28.4 ms, System: 29.4 ms]
          Range (min … max):    56.3 ms …  72.9 ms    40 runs

        Benchmark 5: update-ref: create many refs (refformat = files, refcount = 1000000)
          Time (mean ± σ):     152.752 s ±  0.710 s    [User: 20.315 s, System: 131.310 s]
          Range (min … max):   152.165 s … 153.542 s    3 runs

        Benchmark 6: update-ref: create many refs (refformat = reftable, refcount = 1000000)
          Time (mean ± σ):     51.912 s ±  0.127 s    [User: 26.483 s, System: 25.424 s]
          Range (min … max):   51.769 s … 52.012 s    3 runs

  - Deleting a ref in a fully-packed repository shows that the "files"
    backend scales with the number of refs. The "reftable" backend has
    constant-time deletions.

        Benchmark 1: update-ref: delete ref (refformat = files, refcount = 1)
          Time (mean ± σ):       1.7 ms ±   0.1 ms    [User: 0.4 ms, System: 1.2 ms]
          Range (min … max):     1.6 ms …   2.1 ms    316 runs

        Benchmark 2: update-ref: delete ref (refformat = reftable, refcount = 1)
          Time (mean ± σ):       1.8 ms ±   0.1 ms    [User: 0.4 ms, System: 1.3 ms]
          Range (min … max):     1.7 ms …   2.1 ms    294 runs

        Benchmark 3: update-ref: delete ref (refformat = files, refcount = 1000)
          Time (mean ± σ):       2.0 ms ±   0.1 ms    [User: 0.5 ms, System: 1.4 ms]
          Range (min … max):     1.9 ms …   2.5 ms    287 runs

        Benchmark 4: update-ref: delete ref (refformat = reftable, refcount = 1000)
          Time (mean ± σ):       1.9 ms ±   0.1 ms    [User: 0.5 ms, System: 1.3 ms]
          Range (min … max):     1.8 ms …   2.1 ms    217 runs

        Benchmark 5: update-ref: delete ref (refformat = files, refcount = 1000000)
          Time (mean ± σ):     229.8 ms ±   7.9 ms    [User: 182.6 ms, System: 46.8 ms]
          Range (min … max):   224.6 ms … 245.2 ms    6 runs

        Benchmark 6: update-ref: delete ref (refformat = reftable, refcount = 1000000)
          Time (mean ± σ):       2.0 ms ±   0.0 ms    [User: 0.6 ms, System: 1.3 ms]
          Range (min … max):     2.0 ms …   2.1 ms    3 runs

  - Listing all refs shows no significant advantage for either of the
    backends. The "files" backend is a bit faster, but not by a
    significant margin. When repositories are not packed the "reftable"
    backend outperforms the "files" backend because the "reftable"
    backend performs auto-compaction.

        Benchmark 1: show-ref: print all refs (refformat = files, refcount = 1, packed = true)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.5 ms …   2.0 ms    1729 runs

        Benchmark 2: show-ref: print all refs (refformat = reftable, refcount = 1, packed = true)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.5 ms …   1.8 ms    1816 runs

        Benchmark 3: show-ref: print all refs (refformat = files, refcount = 1000, packed = true)
          Time (mean ± σ):       4.3 ms ±   0.1 ms    [User: 0.9 ms, System: 3.3 ms]
          Range (min … max):     4.1 ms …   4.6 ms    645 runs

        Benchmark 4: show-ref: print all refs (refformat = reftable, refcount = 1000, packed = true)
          Time (mean ± σ):       4.5 ms ±   0.2 ms    [User: 1.0 ms, System: 3.3 ms]
          Range (min … max):     4.2 ms …   5.9 ms    643 runs

        Benchmark 5: show-ref: print all refs (refformat = files, refcount = 1000000, packed = true)
          Time (mean ± σ):      2.537 s ±  0.034 s    [User: 0.488 s, System: 2.048 s]
          Range (min … max):    2.511 s …  2.627 s    10 runs

        Benchmark 6: show-ref: print all refs (refformat = reftable, refcount = 1000000, packed = true)
          Time (mean ± σ):      2.712 s ±  0.017 s    [User: 0.653 s, System: 2.059 s]
          Range (min … max):    2.692 s …  2.752 s    10 runs

        Benchmark 7: show-ref: print all refs (refformat = files, refcount = 1, packed = false)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.5 ms …   1.9 ms    1834 runs

        Benchmark 8: show-ref: print all refs (refformat = reftable, refcount = 1, packed = false)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.4 ms …   2.0 ms    1840 runs

        Benchmark 9: show-ref: print all refs (refformat = files, refcount = 1000, packed = false)
          Time (mean ± σ):      13.8 ms ±   0.2 ms    [User: 2.8 ms, System: 10.8 ms]
          Range (min … max):    13.3 ms …  14.5 ms    208 runs

        Benchmark 10: show-ref: print all refs (refformat = reftable, refcount = 1000, packed = false)
          Time (mean ± σ):       4.5 ms ±   0.2 ms    [User: 1.2 ms, System: 3.3 ms]
          Range (min … max):     4.3 ms …   6.2 ms    624 runs

        Benchmark 11: show-ref: print all refs (refformat = files, refcount = 1000000, packed = false)
          Time (mean ± σ):     12.127 s ±  0.129 s    [User: 2.675 s, System: 9.451 s]
          Range (min … max):   11.965 s … 12.370 s    10 runs

        Benchmark 12: show-ref: print all refs (refformat = reftable, refcount = 1000000, packed = false)
          Time (mean ± σ):      2.799 s ±  0.022 s    [User: 0.735 s, System: 2.063 s]
          Range (min … max):    2.769 s …  2.836 s    10 runs

  - Printing a single ref shows no real difference between the "files"
    and "reftable" backends.

        Benchmark 1: show-ref: print single ref (refformat = files, refcount = 1)
          Time (mean ± σ):       1.5 ms ±   0.1 ms    [User: 0.4 ms, System: 1.0 ms]
          Range (min … max):     1.4 ms …   1.8 ms    1779 runs

        Benchmark 2: show-ref: print single ref (refformat = reftable, refcount = 1)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.4 ms …   2.5 ms    1753 runs

        Benchmark 3: show-ref: print single ref (refformat = files, refcount = 1000)
          Time (mean ± σ):       1.5 ms ±   0.1 ms    [User: 0.3 ms, System: 1.1 ms]
          Range (min … max):     1.4 ms …   1.9 ms    1840 runs

        Benchmark 4: show-ref: print single ref (refformat = reftable, refcount = 1000)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.5 ms …   2.0 ms    1831 runs

        Benchmark 5: show-ref: print single ref (refformat = files, refcount = 1000000)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.5 ms …   2.1 ms    1848 runs

        Benchmark 6: show-ref: print single ref (refformat = reftable, refcount = 1000000)
          Time (mean ± σ):       1.6 ms ±   0.1 ms    [User: 0.4 ms, System: 1.1 ms]
          Range (min … max):     1.5 ms …   2.1 ms    1762 runs

So overall, performance depends on the usecases. Except for many
sequential writes the "reftable" backend is roughly on par or
significantly faster than the "files" backend though. Given that the
"files" backend has received 18 years of optimizations by now this can
be seen as a win. Furthermore, we can expect that the "reftable" backend
will grow faster over time when attention turns more towards
optimizations.

The complete test suite passes, except for those tests explicitly marked
to require the REFFILES prerequisite. Some tests in t0610 are marked as
failing because they depend on still-in-flight bug fixes. Tests can be
run with the new backend by setting the GIT_TEST_DEFAULT_REF_FORMAT
environment variable to "reftable".

There is a single known conceptual incompatibility with the dumb HTTP
transport. As "info/refs" SHOULD NOT contain the HEAD reference, and
because the "HEAD" file is not valid anymore, it is impossible for the
remote client to figure out the default branch without changing the
protocol. This shortcoming needs to be handled in a subsequent patch
series.

As the reftable library has already been introduced a while ago, this
commit message will not go into the details of how exactly the on-disk
format works. Please refer to our preexisting technical documentation at
Documentation/technical/reftable for this.

[1]: https://public-inbox.org/git/CAJo=hJtyof=HRy=2sLP0ng0uZ4=S-DpZ5dR1aF+VHVETKG20OQ@mail.gmail.com/

Original-idea-by: Shawn Pearce <spearce@spearce.org>
Based-on-patch-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-07 08:28:37 -08:00
Junio C Hamano
8282f95928 Merge branch 'ps/not-so-many-refs-are-special'
Define "special ref" as a very narrow set that consists of
FETCH_HEAD and MERGE_HEAD, and clarify everything else that used to
be classified as such are actually just pseudorefs.

* ps/not-so-many-refs-are-special:
  Documentation: add "special refs" to the glossary
  refs: redefine special refs
  refs: convert MERGE_AUTOSTASH to become a normal pseudo-ref
  sequencer: introduce functions to handle autostashes via refs
  refs: convert AUTO_MERGE to become a normal pseudo-ref
  sequencer: delete REBASE_HEAD in correct repo when picking commits
  sequencer: clean up pseudo refs with REF_NO_DEREF
2024-01-29 16:03:00 -08:00
Junio C Hamano
dc8ce995a2 Merge branch 'ps/worktree-refdb-initialization'
Instead of manually creating refs/ hierarchy on disk upon a
creation of a secondary worktree, which is only usable via the
files backend, use the refs API to populate it.

* ps/worktree-refdb-initialization:
  builtin/worktree: create refdb via ref backend
  worktree: expose interface to look up worktree by name
  builtin/worktree: move setup of commondir file earlier
  refs/files: skip creation of "refs/{heads,tags}" for worktrees
  setup: move creation of "refs/" into the files backend
  refs: prepare `refs_init_db()` for initializing worktree refs
2024-01-26 08:54:46 -08:00
Patrick Steinhardt
2cd33f4428 refs: redefine special refs
Now that our list of special refs really only contains refs which have
actually-special semantics, let's redefine what makes a special ref.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-19 11:10:41 -08:00
Patrick Steinhardt
3f921c7591 refs: convert MERGE_AUTOSTASH to become a normal pseudo-ref
Similar to the preceding conversion of the AUTO_MERGE pseudo-ref, let's
convert the MERGE_AUTOSTASH ref to become a normal pseudo-ref as well.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-19 11:10:41 -08:00
Patrick Steinhardt
fd7c6ffa9e refs: convert AUTO_MERGE to become a normal pseudo-ref
In 70c70de616 (refs: complete list of special refs, 2023-12-14) we have
inrtoduced a new `is_special_ref()` function that classifies some refs
as being special. The rule is that special refs are exclusively read and
written via the filesystem directly, whereas normal refs exclucsively go
via the refs API.

The intent of that commit was to record the status quo so that we know
to route reads of such special refs consistently. Eventually, the list
should be reduced to its bare minimum of refs which really are special,
namely FETCH_HEAD and MERGE_HEAD.

Follow up on this promise and convert the AUTO_MERGE ref to become a
normal pseudo-ref by using the refs API to both read and write it
instead of accessing the filesystem directly.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-19 11:10:41 -08:00
Junio C Hamano
32c6fc3e30 Merge branch 'ps/refstorage-extension'
Introduce a new extension "refstorage" so that we can mark a
repository that uses a non-default ref backend, like reftable.

* ps/refstorage-extension:
  t9500: write "extensions.refstorage" into config
  builtin/clone: introduce `--ref-format=` value flag
  builtin/init: introduce `--ref-format=` value flag
  builtin/rev-parse: introduce `--show-ref-format` flag
  t: introduce GIT_TEST_DEFAULT_REF_FORMAT envvar
  setup: introduce GIT_DEFAULT_REF_FORMAT envvar
  setup: introduce "extensions.refStorage" extension
  setup: set repository's formats on init
  setup: start tracking ref storage format
  refs: refactor logic to look up storage backends
  worktree: skip reading HEAD when repairing worktrees
  t: introduce DEFAULT_REPO_FORMAT prereq
2024-01-16 10:11:57 -08:00
Patrick Steinhardt
2e573d61ff refs: prepare refs_init_db() for initializing worktree refs
The purpose of `refs_init_db()` is to initialize the on-disk files of a
new ref database. The function is quite inflexible right now though, as
callers can neither specify the `struct ref_store` nor can they pass any
flags.

Refactor the interface to accept both of these. This will be required so
that we can start initializing per-worktree ref databases via the ref
backend instead of open-coding the initialization in "worktree.c".

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-08 13:17:30 -08:00
Junio C Hamano
dbf668a1b7 Merge branch 'ps/pseudo-refs'
Assorted changes around pseudoref handling.

* ps/pseudo-refs:
  bisect: consistently write BISECT_EXPECTED_REV via the refdb
  refs: complete list of special refs
  refs: propagate errno when reading special refs fails
  wt-status: read HEAD and ORIG_HEAD via the refdb
2024-01-02 13:51:30 -08:00
Patrick Steinhardt
173761e21b setup: start tracking ref storage format
In order to discern which ref storage format a repository is supposed to
use we need to start setting up and/or discovering the format. This
needs to happen in two separate code paths.

  - The first path is when we create a repository via `init_db()`. When
    we are re-initializing a preexisting repository we need to retain
    the previously used ref storage format -- if the user asked for a
    different format then this indicates an error and we error out.
    Otherwise we either initialize the repository with the format asked
    for by the user or the default format, which currently is the
    "files" backend.

  - The second path is when discovering repositories, where we need to
    read the config of that repository. There is not yet any way to
    configure something other than the "files" backend, so we can just
    blindly set the ref storage format to this backend.

Wire up this logic so that we have the ref storage format always readily
available when needed. As there is only a single backend and because it
is not configurable we cannot yet verify that this tracking works as
expected via tests, but tests will be added in subsequent commits. To
countermand this ommission now though, raise a BUG() in case the ref
storage format is not set up properly in `ref_store_init()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-02 09:24:47 -08:00
Patrick Steinhardt
0fcc285c5e refs: refactor logic to look up storage backends
In order to look up ref storage backends, we're currently using a linked
list of backends, where each backend is expected to set up its `next`
pointer to the next ref storage backend. This is kind of a weird setup
as backends need to be aware of other backends without much of a reason.

Refactor the code so that the array of backends is centrally defined in
"refs.c", where each backend is now identified by an integer constant.
Expose functions to translate from those integer constants to the name
and vice versa, which will be required by subsequent patches.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-02 09:24:47 -08:00
Patrick Steinhardt
0a06892ddd bisect: consistently write BISECT_EXPECTED_REV via the refdb
We're inconsistently writing BISECT_EXPECTED_REV both via the filesystem
and via the refdb, which violates the newly established rules for how
special refs must be treated. This works alright in practice with the
reffiles reference backend, but will cause bugs once we gain additional
backends.

Fix this issue and consistently write BISECT_EXPECTED_REV via the refdb
so that it is no longer a special ref.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-14 09:25:27 -08:00
Patrick Steinhardt
70c70de616 refs: complete list of special refs
We have some references that are more special than others. The reason
for them being special is that they either do not follow the usual
format of references, or that they are written to the filesystem
directly by the respective owning subsystem and thus circumvent the
reference backend.

This works perfectly fine right now because the reffiles backend will
know how to read those refs just fine. But with the prospect of gaining
a new reference backend implementation we need to be a lot more careful
here:

  - We need to make sure that we are consistent about how those refs are
    written. They must either always be written via the filesystem, or
    they must always be written via the reference backend. Any mixture
    will lead to inconsistent state.

  - We need to make sure that such special refs are always handled
    specially when reading them.

We're already mostly good with regard to the first item, except for
`BISECT_EXPECTED_REV` which will be addressed in a subsequent commit.
But the current list of special refs is missing some refs that really
should be treated specially. Right now, we only treat `FETCH_HEAD` and
`MERGE_HEAD` specially here.

Introduce a new function `is_special_ref()` that contains all current
instances of special refs to fix the reading path.

Note that this is only a temporary measure where we record and rectify
the current state. Ideally, the list of special refs should in the end
only contain `FETCH_HEAD` and `MERGE_HEAD` again because they both may
reference multiple objects and can contain annotations, so they indeed
are special.

Based-on-patch-by: Han-Wen Nienhuys <hanwenn@gmail.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-14 09:25:27 -08:00
Patrick Steinhardt
668cdc043f refs: propagate errno when reading special refs fails
Some refs in Git are more special than others due to reasons explained
in the next commit. These refs are read via `refs_read_special_head()`,
but this function doesn't behave the same as when we try to read a
normal ref. Most importantly, we do not propagate `failure_errno` in the
case where the reference does not exist, which is behaviour that we rely
on in many parts of Git.

Fix this bug by propagating errno when `strbuf_read_file()` fails.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-14 09:25:26 -08:00
Patrick Steinhardt
d6f8e72982 refs: deduplicate code to delete references
Both the files and the packed-refs reference backends now use the same
generic transactions-based code to delete references. Let's pull these
implementations up into `refs_delete_refs()` to deduplicate the code.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-17 10:12:12 +09:00
Junio C Hamano
c5fcd34e1b Merge branch 'jk/unused-parameter'
Mark-up unused parameters in the code so that we can eventually
enable -Wunused-parameter by default.

* jk/unused-parameter:
  t/helper: mark unused callback void data parameters
  tag: mark unused parameters in each_tag_name_fn callbacks
  rev-parse: mark unused parameter in for_each_abbrev callback
  replace: mark unused parameter in each_mergetag_fn callback
  replace: mark unused parameter in ref callback
  merge-tree: mark unused parameter in traverse callback
  fsck: mark unused parameters in various fsck callbacks
  revisions: drop unused "opt" parameter in "tweak" callbacks
  count-objects: mark unused parameter in alternates callback
  am: mark unused keep_cr parameters
  http-push: mark unused parameter in xml callback
  http: mark unused parameters in curl callbacks
  do_for_each_ref_helper(): mark unused repository parameter
  test-ref-store: drop unimplemented reflog-expire command
2023-07-25 12:05:24 -07:00
Junio C Hamano
39fe402d67 Merge branch 'tb/refs-exclusion-and-packed-refs'
Enumerating refs in the packed-refs file, while excluding refs that
match certain patterns, has been optimized.

* tb/refs-exclusion-and-packed-refs:
  ls-refs.c: avoid enumerating hidden refs where possible
  upload-pack.c: avoid enumerating hidden refs where possible
  builtin/receive-pack.c: avoid enumerating hidden references
  refs.h: implement `hidden_refs_to_excludes()`
  refs.h: let `for_each_namespaced_ref()` take excluded patterns
  revision.h: store hidden refs in a `strvec`
  refs/packed-backend.c: add trace2 counters for jump list
  refs/packed-backend.c: implement jump lists to avoid excluded pattern(s)
  refs/packed-backend.c: refactor `find_reference_location()`
  refs: plumb `exclude_patterns` argument throughout
  builtin/for-each-ref.c: add `--exclude` option
  ref-filter.c: parameterize match functions over patterns
  ref-filter: add `ref_filter_clear()`
  ref-filter: clear reachable list pointers after freeing
  ref-filter.h: provide `REF_FILTER_INIT`
  refs.c: rename `ref_filter`
2023-07-21 13:47:26 -07:00
Jeff King
1779deed39 do_for_each_ref_helper(): mark unused repository parameter
This function gets a repository parameter because it's a callback for
do_for_each_repo_ref_iterator(). But it's just a wrapper that passes
along each call to a regular each_ref_fn callback, and the latter
doesn't accept a repository argument.

Probably in the long run all of the each_ref_fn callbacks should get a
repository parameter, too. But changing that now would require updates
all over the code base. Until that happens, let's annotate this wrapper
callback to quiet the compiler's -Wunused-parameter warning.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-13 17:23:59 -07:00
Taylor Blau
15af64dcfd refs.h: implement hidden_refs_to_excludes()
In subsequent commits, we'll teach `receive-pack` and `upload-pack` to
use the new jump list feature in the packed-refs iterator by ignoring
references which are mentioned via its respective hideRefs lists.

However, the packed-ref jump lists cannot handle un-hiding rules (that
begin with '!'), or namespace comparisons (that begin with '^'). Add a
convenience function to the refs.h API to detect when either of these
conditions are met, and returns an appropriate value to pass as excluded
patterns.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:56 -07:00
Taylor Blau
e6bf24d39a refs.h: let for_each_namespaced_ref() take excluded patterns
A future commit will want to call `for_each_namespaced_ref()` with
a list of excluded patterns.

We could introduce a variant of that function, say,
`for_each_namespaced_ref_exclude()` which takes the extra parameter, and
reimplement the original function in terms of that. But all but one
caller (in `http-backend.c`) will supply the new parameter, so add the
new parameter to `for_each_namespaced_ref()` itself instead of
introducing a new function.

For now, supply NULL for the list of excluded patterns at all callers to
avoid changing behavior, which we will do in a future change.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:56 -07:00
Taylor Blau
c45841fff8 revision.h: store hidden refs in a strvec
In subsequent commits, it will be convenient to have a 'const char **'
of hidden refs (matching `transfer.hiderefs`, `uploadpack.hideRefs`,
etc.), instead of a `string_list`.

Convert spots throughout the tree that store the list of hidden refs
from a `string_list` to a `strvec`.

Note that in `parse_hide_refs_config()` there is an ugly const-cast used
to avoid an extra copy of each value before trimming any trailing slash
characters. This could instead be written as:

    ref = xstrdup(value);
    len = strlen(ref);
    while (len && ref[len - 1] == '/')
            ref[--len] = '\0';
    strvec_push(hide_refs, ref);
    free(ref);

but the double-copy (once when calling `xstrdup()`, and another via
`strvec_push()`) is wasteful.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:56 -07:00
Taylor Blau
b269ac53c0 refs: plumb exclude_patterns argument throughout
The subsequent patch will want to access an optional `excluded_patterns`
array within `refs/packed-backend.c` that will cull out certain
references matching any of the given patterns on a best-effort basis.

To do so, the refs subsystem needs to be updated to pass this value
across a number of different locations.

Prepare for a future patch by introducing this plumbing now, passing
NULLs at top-level APIs in order to make that patch less noisy and more
easily readable.

Signed-off-by: Taylor Blau <me@ttaylorr.co>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:55 -07:00
Jeff King
bf1377a12b refs.c: rename ref_filter
The refs machinery has its own implementation of a `ref_filter` (used by
`for-each-ref`), which is distinct from the `ref-filter.h` API (also
used by `for-each-ref`, among other things).

Rename the one within refs.c to more clearly indicate its purpose.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-10 14:48:55 -07:00
Calvin Wan
91c080dff5 git-compat-util: move alloc macros to git-compat-util.h
alloc_nr, ALLOC_GROW, and ALLOC_GROW_BY are commonly used macros for
dynamic array allocation. Moving these macros to git-compat-util.h with
the other alloc macros focuses alloc.[ch] to allocation for Git objects
and additionally allows us to remove inclusions to alloc.h from files
that solely used the above macros.

Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-05 11:42:31 -07:00
Calvin Wan
da9502ff4d treewide: remove unnecessary includes for wrapper.h
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-05 11:41:59 -07:00
Elijah Newren
a034e9106f object-store-ll.h: split this header out of object-store.h
The vast majority of files including object-store.h did not need dir.h
nor khash.h.  Split the header into two files, and let most just depend
upon object-store-ll.h, while letting the two callers that need it
depend on the full object-store.h.

After this patch:
    $ git grep -h include..object-store | sort | uniq -c
          2 #include "object-store.h"
        129 #include "object-store-ll.h"

Diff best viewed with `--color-moved`.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-06-21 13:39:54 -07:00
Elijah Newren
dd77d58795 git-compat-util.h: remove unneccessary include of wildmatch.h
The include of wildmatch.h in git-compat-util.h was added in cebcab189a
(Makefile: add USE_WILDMATCH to use wildmatch as fnmatch, 2013-01-01) as
a way to be able to compile-time force any calls to fnmatch() to instead
invoke wildmatch().  The defines and inline function were removed in
70a8fc999d (stop using fnmatch (either native or compat), 2014-02-15),
and this include in git-compat-util.h has been unnecessary ever since.

Remove the include from git-compat-util.h, but add it to the .c files
that had omitted the direct #include they needed.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-06-21 13:39:54 -07:00
Elijah Newren
c339932bd8 repository: remove unnecessary include of path.h
This also made it clear that several .c files that depended upon path.h
were missing a #include for it; add the missing includes while at it.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-06-21 13:39:53 -07:00
John Cai
826ae79fca pack-refs: teach --exclude option to exclude refs from being packed
At GitLab, we have a system that creates ephemeral internal refs that
don't live long before getting deleted. Having an option to exclude
certain refs from a packed-refs file allows these internal references to
be deleted much more efficiently.

Add an --exclude option to the pack-refs builtin, and use the ref
exclusions API to exclude certain refs from being packed into the final
packed-refs file

Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-05-12 14:54:14 -07:00
Elijah Newren
e93fc5d721 treewide: remove cache.h inclusion due to object-name.h changes
Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-04-11 08:52:09 -07:00
Elijah Newren
dabab1d6e6 object-name.h: move declarations for object-name.c functions from cache.h
Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-04-11 08:52:09 -07:00
Elijah Newren
6c6ddf92d5 treewide: be explicit about dependence on advice.h
Dozens of files made use of advice functions, without explicitly
including advice.h.  This made it more difficult to find which files
could remove a dependence on cache.h.  Make C files explicitly include
advice.h if they are using it.

Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-04-11 08:52:09 -07:00
Junio C Hamano
e7dca80692 Merge branch 'ab/remove-implicit-use-of-the-repository' into en/header-split-cache-h
* ab/remove-implicit-use-of-the-repository:
  libs: use "struct repository *" argument, not "the_repository"
  post-cocci: adjust comments for recent repo_* migration
  cocci: apply the "revision.h" part of "the_repository.pending"
  cocci: apply the "rerere.h" part of "the_repository.pending"
  cocci: apply the "refs.h" part of "the_repository.pending"
  cocci: apply the "promisor-remote.h" part of "the_repository.pending"
  cocci: apply the "packfile.h" part of "the_repository.pending"
  cocci: apply the "pretty.h" part of "the_repository.pending"
  cocci: apply the "object-store.h" part of "the_repository.pending"
  cocci: apply the "diff.h" part of "the_repository.pending"
  cocci: apply the "commit.h" part of "the_repository.pending"
  cocci: apply the "commit-reach.h" part of "the_repository.pending"
  cocci: apply the "cache.h" part of "the_repository.pending"
  cocci: add missing "the_repository" macros to "pending"
  cocci: sort "the_repository" rules by header
  cocci: fix incorrect & verbose "the_repository" rules
  cocci: remove dead rule from "the_repository.pending.cocci"
2023-04-04 08:25:52 -07:00
Ævar Arnfjörð Bjarmason
c7c33f50bd post-cocci: adjust comments for recent repo_* migration
In preceding commits we changed many calls to macros that were
providing a "the_repository" argument to invoke corresponding repo_*()
function instead. Let's follow-up and adjust references to those in
comments, which coccinelle didn't (and inherently can't) catch.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-28 07:36:46 -07:00
Elijah Newren
e38da487cc setup.h: move declarations for setup.c functions from cache.h
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-21 10:56:54 -07:00
Elijah Newren
32a8f51061 environment.h: move declarations for environment.c functions from cache.h
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-21 10:56:53 -07:00
Elijah Newren
d5ebb50dcb wrapper.h: move declarations for wrapper.c functions from cache.h
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-21 10:56:53 -07:00
Elijah Newren
f394e093df treewide: be explicit about dependence on gettext.h
Dozens of files made use of gettext functions, without explicitly
including gettext.h.  This made it more difficult to find which files
could remove a dependence on cache.h.  Make C files explicitly include
gettext.h if they are using it.

However, while compat/fsmonitor/fsm-ipc-darwin.c should also gain an
include of gettext.h, it was left out to avoid conflicting with an
in-flight topic.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-21 10:56:51 -07:00
Elijah Newren
a6dc3d364c treewide: remove unnecessary cache.h inclusion from a few headers
Ever since a64215b6cd ("object.h: stop depending on cache.h; make
cache.h depend on object.h", 2023-02-24), we have a few headers that
could have replaced their include of cache.h with an include of
object.h.  Make that change now.

Some C files had to start including cache.h after this change (or some
smaller header it had brought in), because the C files were depending
on things from cache.h but were only formerly implicitly getting
cache.h through one of these headers being modified in this patch.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-03-21 10:56:50 -07:00