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refs: add support for transactional symref updates

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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>
This commit is contained in:
Karthik Nayak
2024-05-07 14:58:56 +02:00
committed by Junio C Hamano
parent e9965ba477
commit 644daf7785
4 changed files with 196 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

113
refs/files-backend.c
View File

@ -2394,8 +2394,9 @@ static int split_symref_update(struct ref_update *update,
new_update = ref_transaction_add_update(
transaction, referent, new_flags,
&update->new_oid, &update->old_oid,
NULL, NULL, update->msg);
update->new_target ? NULL : &update->new_oid,
update->old_target ? NULL : &update->old_oid,
update->new_target, update->old_target, update->msg);
new_update->parent_update = update;
@ -2483,7 +2484,7 @@ static int lock_ref_for_update(struct files_ref_store *refs,
files_assert_main_repository(refs, "lock_ref_for_update");
if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
if ((update->flags & REF_HAVE_NEW) && ref_update_has_null_new_value(update))
update->flags |= REF_DELETING;
if (head_ref) {
@ -2526,7 +2527,14 @@ static int lock_ref_for_update(struct files_ref_store *refs,
ret = TRANSACTION_GENERIC_ERROR;
goto out;
}
} else if (check_old_oid(update, &lock->old_oid, err)) {
}
if (update->old_target) {
if (ref_update_check_old_target(referent.buf, update, err)) {
ret = TRANSACTION_GENERIC_ERROR;
goto out;
}
} else if (check_old_oid(update, &lock->old_oid, err)) {
ret = TRANSACTION_GENERIC_ERROR;
goto out;
}
@ -2547,7 +2555,17 @@ static int lock_ref_for_update(struct files_ref_store *refs,
} else {
struct ref_update *parent_update;
if (check_old_oid(update, &lock->old_oid, err)) {
/*
* Even if the ref is a regular ref, if `old_target` is set, we
* check the referent value. Ideally `old_target` should only
* be set for symrefs, but we're strict about its usage.
*/
if (update->old_target) {
if (ref_update_check_old_target(referent.buf, update, err)) {
ret = TRANSACTION_GENERIC_ERROR;
goto out;
}
} else if (check_old_oid(update, &lock->old_oid, err)) {
ret = TRANSACTION_GENERIC_ERROR;
goto out;
}
@ -2565,9 +2583,28 @@ static int lock_ref_for_update(struct files_ref_store *refs,
}
}
if ((update->flags & REF_HAVE_NEW) &&
!(update->flags & REF_DELETING) &&
!(update->flags & REF_LOG_ONLY)) {
if (update->new_target && !(update->flags & REF_LOG_ONLY)) {
if (create_symref_lock(refs, lock, update->refname,
update->new_target, err)) {
ret = TRANSACTION_GENERIC_ERROR;
goto out;
}
if (close_ref_gently(lock)) {
strbuf_addf(err, "couldn't close '%s.lock'",
update->refname);
ret = TRANSACTION_GENERIC_ERROR;
goto out;
}
/*
* Once we have created the symref lock, the commit
* phase of the transaction only needs to commit the lock.
*/
update->flags |= REF_NEEDS_COMMIT;
} else if ((update->flags & REF_HAVE_NEW) &&
!(update->flags & REF_DELETING) &&
!(update->flags & REF_LOG_ONLY)) {
if (!(update->type & REF_ISSYMREF) &&
oideq(&lock->old_oid, &update->new_oid)) {
/*
@ -2830,6 +2867,43 @@ cleanup:
return ret;
}
static int parse_and_write_reflog(struct files_ref_store *refs,
struct ref_update *update,
struct ref_lock *lock,
struct strbuf *err)
{
if (update->new_target) {
/*
* We want to get the resolved OID for the target, to ensure
* that the correct value is added to the reflog.
*/
if (!refs_resolve_ref_unsafe(&refs->base, update->new_target,
RESOLVE_REF_READING,
&update->new_oid, NULL)) {
/*
* TODO: currently we skip creating reflogs for dangling
* symref updates. It would be nice to capture this as
* zero oid updates however.
*/
return 0;
}
}
if (files_log_ref_write(refs, lock->ref_name, &lock->old_oid,
&update->new_oid, update->msg, update->flags, err)) {
char *old_msg = strbuf_detach(err, NULL);
strbuf_addf(err, "cannot update the ref '%s': %s",
lock->ref_name, old_msg);
free(old_msg);
unlock_ref(lock);
update->backend_data = NULL;
return -1;
}
return 0;
}
static int files_transaction_finish(struct ref_store *ref_store,
struct ref_transaction *transaction,
struct strbuf *err)
@ -2860,23 +2934,20 @@ static int files_transaction_finish(struct ref_store *ref_store,
if (update->flags & REF_NEEDS_COMMIT ||
update->flags & REF_LOG_ONLY) {
if (files_log_ref_write(refs,
lock->ref_name,
&lock->old_oid,
&update->new_oid,
update->msg, update->flags,
err)) {
char *old_msg = strbuf_detach(err, NULL);
strbuf_addf(err, "cannot update the ref '%s': %s",
lock->ref_name, old_msg);
free(old_msg);
unlock_ref(lock);
update->backend_data = NULL;
if (parse_and_write_reflog(refs, update, lock, err)) {
ret = TRANSACTION_GENERIC_ERROR;
goto cleanup;
}
}
/*
* We try creating a symlink, if that succeeds we continue to the
* next update. If not, we try and create a regular symref.
*/
if (update->new_target && prefer_symlink_refs)
if (!create_ref_symlink(lock, update->new_target))
continue;
if (update->flags & REF_NEEDS_COMMIT) {
clear_loose_ref_cache(refs);
if (commit_ref(lock)) {