mirrors/git
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

docs: move protocol-related docs to man section 5

Browse Source 
Continue the move of existing Documentation/technical/* protocol and
file-format documentation into our main documentation space. By moving
the things that discuss the protocol we can properly link from
e.g. lsrefs.unborn and protocol.version documentation to a manpage we
build by default.

So far we have been using the "gitformat-" prefix for the
documentation we've been moving over from Documentation/technical/*,
but for protocol documentation let's use "gitprotocol-*".

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Ævar Arnfjörð Bjarmason
2022-08-04 18:28:36 +02:00
committed by Junio C Hamano
parent 8cbace93d2
commit 5db921054e
17 changed files with 106 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/technical/api-simple-ipc.txt
View File

@ -78,7 +78,7 @@ client and an optional response message from the server. Both the
client and server messages are unlimited in length and are terminated
with a flush packet.
The pkt-line routines (Documentation/technical/protocol-common.txt)
The pkt-line routines (linkgit:gitprotocol-common[5])
are used to simplify buffer management during message generation,
transmission, and reception. A flush packet is used to mark the end
of the message. This allows the sender to incrementally generate and

6
Documentation/technical/http-protocol.txt
View File

@ -222,7 +222,7 @@ smart server reply:
S: 0000
The client may send Extra Parameters (see
Documentation/technical/pack-protocol.txt) as a colon-separated string
linkgit:gitprotocol-pack[5]) as a colon-separated string
in the Git-Protocol HTTP header.
Uses the `--http-backend-info-refs` option to
@ -518,5 +518,5 @@ References
http://www.ietf.org/rfc/rfc1738.txt[RFC 1738: Uniform Resource Locators (URL)]
http://www.ietf.org/rfc/rfc2616.txt[RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1]
link:technical/pack-protocol.html
link:technical/protocol-capabilities.html
linkgit:gitprotocol-pack[5]
linkgit:gitprotocol-capabilities[5]

2
Documentation/technical/long-running-process-protocol.txt
View File

@ -3,7 +3,7 @@ Long-running process protocol
This protocol is used when Git needs to communicate with an external
process throughout the entire life of a single Git command. All
communication is in pkt-line format (see technical/protocol-common.txt)
communication is in pkt-line format (see linkgit:gitprotocol-common[5])
over standard input and standard output.
Handshake

709
Documentation/technical/pack-protocol.txt
View File

@ -1,709 +0,0 @@
Packfile transfer protocols
===========================
Git supports transferring data in packfiles over the ssh://, git://, http:// and
file:// transports. There exist two sets of protocols, one for pushing
data from a client to a server and another for fetching data from a
server to a client. The three transports (ssh, git, file) use the same
protocol to transfer data. http is documented in http-protocol.txt.
The processes invoked in the canonical Git implementation are 'upload-pack'
on the server side and 'fetch-pack' on the client side for fetching data;
then 'receive-pack' on the server and 'send-pack' on the client for pushing
data. The protocol functions to have a server tell a client what is
currently on the server, then for the two to negotiate the smallest amount
of data to send in order to fully update one or the other.
pkt-line Format
---------------
The descriptions below build on the pkt-line format described in
protocol-common.txt. When the grammar indicate `PKT-LINE(...)`, unless
otherwise noted the usual pkt-line LF rules apply: the sender SHOULD
include a LF, but the receiver MUST NOT complain if it is not present.
An error packet is a special pkt-line that contains an error string.
----
error-line = PKT-LINE("ERR" SP explanation-text)
----
Throughout the protocol, where `PKT-LINE(...)` is expected, an error packet MAY
be sent. Once this packet is sent by a client or a server, the data transfer
process defined in this protocol is terminated.
Transports
----------
There are three transports over which the packfile protocol is
initiated. The Git transport is a simple, unauthenticated server that
takes the command (almost always 'upload-pack', though Git
servers can be configured to be globally writable, in which 'receive-
pack' initiation is also allowed) with which the client wishes to
communicate and executes it and connects it to the requesting
process.
In the SSH transport, the client just runs the 'upload-pack'
or 'receive-pack' process on the server over the SSH protocol and then
communicates with that invoked process over the SSH connection.
The file:// transport runs the 'upload-pack' or 'receive-pack'
process locally and communicates with it over a pipe.
Extra Parameters
----------------
The protocol provides a mechanism in which clients can send additional
information in its first message to the server. These are called "Extra
Parameters", and are supported by the Git, SSH, and HTTP protocols.
Each Extra Parameter takes the form of `<key>=<value>` or `<key>`.
Servers that receive any such Extra Parameters MUST ignore all
unrecognized keys. Currently, the only Extra Parameter recognized is
"version" with a value of '1' or '2'. See protocol-v2.txt for more
information on protocol version 2.
Git Transport
-------------
The Git transport starts off by sending the command and repository
on the wire using the pkt-line format, followed by a NUL byte and a
hostname parameter, terminated by a NUL byte.
0033git-upload-pack /project.git\0host=myserver.com\0
The transport may send Extra Parameters by adding an additional NUL
byte, and then adding one or more NUL-terminated strings:
003egit-upload-pack /project.git\0host=myserver.com\0\0version=1\0
--
git-proto-request = request-command SP pathname NUL
[ host-parameter NUL ] [ NUL extra-parameters ]
request-command = "git-upload-pack" / "git-receive-pack" /
"git-upload-archive" ; case sensitive
pathname = *( %x01-ff ) ; exclude NUL
host-parameter = "host=" hostname [ ":" port ]
extra-parameters = 1*extra-parameter
extra-parameter = 1*( %x01-ff ) NUL
--
host-parameter is used for the
git-daemon name based virtual hosting. See --interpolated-path
option to git daemon, with the %H/%CH format characters.
Basically what the Git client is doing to connect to an 'upload-pack'
process on the server side over the Git protocol is this:
$ echo -e -n \
"003agit-upload-pack /schacon/gitbook.git\0host=example.com\0" |
nc -v example.com 9418
SSH Transport
-------------
Initiating the upload-pack or receive-pack processes over SSH is
executing the binary on the server via SSH remote execution.
It is basically equivalent to running this:
$ ssh git.example.com "git-upload-pack '/project.git'"
For a server to support Git pushing and pulling for a given user over
SSH, that user needs to be able to execute one or both of those
commands via the SSH shell that they are provided on login. On some
systems, that shell access is limited to only being able to run those
two commands, or even just one of them.
In an ssh:// format URI, it's absolute in the URI, so the '/' after
the host name (or port number) is sent as an argument, which is then
read by the remote git-upload-pack exactly as is, so it's effectively
an absolute path in the remote filesystem.
git clone ssh://user@example.com/project.git
|
v
ssh user@example.com "git-upload-pack '/project.git'"
In a "user@host:path" format URI, its relative to the user's home
directory, because the Git client will run:
git clone user@example.com:project.git
|
v
ssh user@example.com "git-upload-pack 'project.git'"
The exception is if a '~' is used, in which case
we execute it without the leading '/'.
ssh://user@example.com/~alice/project.git,
|
v
ssh user@example.com "git-upload-pack '~alice/project.git'"
Depending on the value of the `protocol.version` configuration variable,
Git may attempt to send Extra Parameters as a colon-separated string in
the GIT_PROTOCOL environment variable. This is done only if
the `ssh.variant` configuration variable indicates that the ssh command
supports passing environment variables as an argument.
A few things to remember here:
- The "command name" is spelled with dash (e.g. git-upload-pack), but
this can be overridden by the client;
- The repository path is always quoted with single quotes.
Fetching Data From a Server
---------------------------
When one Git repository wants to get data that a second repository
has, the first can 'fetch' from the second. This operation determines
what data the server has that the client does not then streams that
data down to the client in packfile format.
Reference Discovery
-------------------
When the client initially connects the server will immediately respond
with a version number (if "version=1" is sent as an Extra Parameter),
and a listing of each reference it has (all branches and tags) along
with the object name that each reference currently points to.
$ echo -e -n "0045git-upload-pack /schacon/gitbook.git\0host=example.com\0\0version=1\0" |
nc -v example.com 9418
000eversion 1
00887217a7c7e582c46cec22a130adf4b9d7d950fba0 HEAD\0multi_ack thin-pack
side-band side-band-64k ofs-delta shallow no-progress include-tag
00441d3fcd5ced445d1abc402225c0b8a1299641f497 refs/heads/integration
003f7217a7c7e582c46cec22a130adf4b9d7d950fba0 refs/heads/master
003cb88d2441cac0977faf98efc80305012112238d9d refs/tags/v0.9
003c525128480b96c89e6418b1e40909bf6c5b2d580f refs/tags/v1.0
003fe92df48743b7bc7d26bcaabfddde0a1e20cae47c refs/tags/v1.0^{}
0000
The returned response is a pkt-line stream describing each ref and
its current value. The stream MUST be sorted by name according to
the C locale ordering.
If HEAD is a valid ref, HEAD MUST appear as the first advertised
ref. If HEAD is not a valid ref, HEAD MUST NOT appear in the
advertisement list at all, but other refs may still appear.
The stream MUST include capability declarations behind a NUL on the
first ref. The peeled value of a ref (that is "ref^{}") MUST be
immediately after the ref itself, if presented. A conforming server
MUST peel the ref if it's an annotated tag.
----
advertised-refs = *1("version 1")
(no-refs / list-of-refs)
*shallow
flush-pkt
no-refs = PKT-LINE(zero-id SP "capabilities^{}"
NUL capability-list)
list-of-refs = first-ref *other-ref
first-ref = PKT-LINE(obj-id SP refname
NUL capability-list)
other-ref = PKT-LINE(other-tip / other-peeled)
other-tip = obj-id SP refname
other-peeled = obj-id SP refname "^{}"
shallow = PKT-LINE("shallow" SP obj-id)
capability-list = capability *(SP capability)
capability = 1*(LC_ALPHA / DIGIT / "-" / "_")
LC_ALPHA = %x61-7A
----
Server and client MUST use lowercase for obj-id, both MUST treat obj-id
as case-insensitive.
See protocol-capabilities.txt for a list of allowed server capabilities
and descriptions.
Packfile Negotiation
--------------------
After reference and capabilities discovery, the client can decide to
terminate the connection by sending a flush-pkt, telling the server it can
now gracefully terminate, and disconnect, when it does not need any pack
data. This can happen with the ls-remote command, and also can happen when
the client already is up to date.
Otherwise, it enters the negotiation phase, where the client and
server determine what the minimal packfile necessary for transport is,
by telling the server what objects it wants, its shallow objects
(if any), and the maximum commit depth it wants (if any). The client
will also send a list of the capabilities it wants to be in effect,
out of what the server said it could do with the first 'want' line.
----
upload-request = want-list
*shallow-line
*1depth-request
[filter-request]
flush-pkt
want-list = first-want
*additional-want
shallow-line = PKT-LINE("shallow" SP obj-id)
depth-request = PKT-LINE("deepen" SP depth) /
PKT-LINE("deepen-since" SP timestamp) /
PKT-LINE("deepen-not" SP ref)
first-want = PKT-LINE("want" SP obj-id SP capability-list)
additional-want = PKT-LINE("want" SP obj-id)
depth = 1*DIGIT
filter-request = PKT-LINE("filter" SP filter-spec)
----
Clients MUST send all the obj-ids it wants from the reference
discovery phase as 'want' lines. Clients MUST send at least one
'want' command in the request body. Clients MUST NOT mention an
obj-id in a 'want' command which did not appear in the response
obtained through ref discovery.
The client MUST write all obj-ids which it only has shallow copies
of (meaning that it does not have the parents of a commit) as
'shallow' lines so that the server is aware of the limitations of
the client's history.
The client now sends the maximum commit history depth it wants for
this transaction, which is the number of commits it wants from the
tip of the history, if any, as a 'deepen' line. A depth of 0 is the
same as not making a depth request. The client does not want to receive
any commits beyond this depth, nor does it want objects needed only to
complete those commits. Commits whose parents are not received as a
result are defined as shallow and marked as such in the server. This
information is sent back to the client in the next step.
The client can optionally request that pack-objects omit various
objects from the packfile using one of several filtering techniques.
These are intended for use with partial clone and partial fetch
operations. An object that does not meet a filter-spec value is
omitted unless explicitly requested in a 'want' line. See `rev-list`
for possible filter-spec values.
Once all the 'want's and 'shallow's (and optional 'deepen') are
transferred, clients MUST send a flush-pkt, to tell the server side
that it is done sending the list.
Otherwise, if the client sent a positive depth request, the server
will determine which commits will and will not be shallow and
send this information to the client. If the client did not request
a positive depth, this step is skipped.
----
shallow-update = *shallow-line
*unshallow-line
flush-pkt
shallow-line = PKT-LINE("shallow" SP obj-id)
unshallow-line = PKT-LINE("unshallow" SP obj-id)
----
If the client has requested a positive depth, the server will compute
the set of commits which are no deeper than the desired depth. The set
of commits start at the client's wants.
The server writes 'shallow' lines for each
commit whose parents will not be sent as a result. The server writes
an 'unshallow' line for each commit which the client has indicated is
shallow, but is no longer shallow at the currently requested depth
(that is, its parents will now be sent). The server MUST NOT mark
as unshallow anything which the client has not indicated was shallow.
Now the client will send a list of the obj-ids it has using 'have'
lines, so the server can make a packfile that only contains the objects
that the client needs. In multi_ack mode, the canonical implementation
will send up to 32 of these at a time, then will send a flush-pkt. The
canonical implementation will skip ahead and send the next 32 immediately,
so that there is always a block of 32 "in-flight on the wire" at a time.
----
upload-haves = have-list
compute-end
have-list = *have-line
have-line = PKT-LINE("have" SP obj-id)
compute-end = flush-pkt / PKT-LINE("done")
----
If the server reads 'have' lines, it then will respond by ACKing any
of the obj-ids the client said it had that the server also has. The
server will ACK obj-ids differently depending on which ack mode is
chosen by the client.
In multi_ack mode:
* the server will respond with 'ACK obj-id continue' for any common
commits.
* once the server has found an acceptable common base commit and is
ready to make a packfile, it will blindly ACK all 'have' obj-ids
back to the client.
* the server will then send a 'NAK' and then wait for another response
from the client - either a 'done' or another list of 'have' lines.
In multi_ack_detailed mode:
* the server will differentiate the ACKs where it is signaling
that it is ready to send data with 'ACK obj-id ready' lines, and
signals the identified common commits with 'ACK obj-id common' lines.
Without either multi_ack or multi_ack_detailed:
* upload-pack sends "ACK obj-id" on the first common object it finds.
After that it says nothing until the client gives it a "done".
* upload-pack sends "NAK" on a flush-pkt if no common object
has been found yet. If one has been found, and thus an ACK
was already sent, it's silent on the flush-pkt.
After the client has gotten enough ACK responses that it can determine
that the server has enough information to send an efficient packfile
(in the canonical implementation, this is determined when it has received
enough ACKs that it can color everything left in the --date-order queue
as common with the server, or the --date-order queue is empty), or the
client determines that it wants to give up (in the canonical implementation,
this is determined when the client sends 256 'have' lines without getting
any of them ACKed by the server - meaning there is nothing in common and
the server should just send all of its objects), then the client will send
a 'done' command. The 'done' command signals to the server that the client
is ready to receive its packfile data.
However, the 256 limit *only* turns on in the canonical client
implementation if we have received at least one "ACK %s continue"
during a prior round. This helps to ensure that at least one common
ancestor is found before we give up entirely.
Once the 'done' line is read from the client, the server will either
send a final 'ACK obj-id' or it will send a 'NAK'. 'obj-id' is the object
name of the last commit determined to be common. The server only sends
ACK after 'done' if there is at least one common base and multi_ack or
multi_ack_detailed is enabled. The server always sends NAK after 'done'
if there is no common base found.
Instead of 'ACK' or 'NAK', the server may send an error message (for
example, if it does not recognize an object in a 'want' line received
from the client).
Then the server will start sending its packfile data.
----
server-response = *ack_multi ack / nak
ack_multi = PKT-LINE("ACK" SP obj-id ack_status)
ack_status = "continue" / "common" / "ready"
ack = PKT-LINE("ACK" SP obj-id)
nak = PKT-LINE("NAK")
----
A simple clone may look like this (with no 'have' lines):
----
C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \
side-band-64k ofs-delta\n
C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n
C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n
C: 0032want 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n
C: 0032want 74730d410fcb6603ace96f1dc55ea6196122532d\n
C: 0000
C: 0009done\n
S: 0008NAK\n
S: [PACKFILE]
----
An incremental update (fetch) response might look like this:
----
C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \
side-band-64k ofs-delta\n
C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n
C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n
C: 0000
C: 0032have 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n
C: [30 more have lines]
C: 0032have 74730d410fcb6603ace96f1dc55ea6196122532d\n
C: 0000
S: 003aACK 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01 continue\n
S: 003aACK 74730d410fcb6603ace96f1dc55ea6196122532d continue\n
S: 0008NAK\n
C: 0009done\n
S: 0031ACK 74730d410fcb6603ace96f1dc55ea6196122532d\n
S: [PACKFILE]
----
Packfile Data
-------------
Now that the client and server have finished negotiation about what
the minimal amount of data that needs to be sent to the client is, the server
will construct and send the required data in packfile format.
See pack-format.txt for what the packfile itself actually looks like.
If 'side-band' or 'side-band-64k' capabilities have been specified by
the client, the server will send the packfile data multiplexed.
Each packet starting with the packet-line length of the amount of data
that follows, followed by a single byte specifying the sideband the
following data is coming in on.
In 'side-band' mode, it will send up to 999 data bytes plus 1 control
code, for a total of up to 1000 bytes in a pkt-line. In 'side-band-64k'
mode it will send up to 65519 data bytes plus 1 control code, for a
total of up to 65520 bytes in a pkt-line.
The sideband byte will be a '1', '2' or a '3'. Sideband '1' will contain
packfile data, sideband '2' will be used for progress information that the
client will generally print to stderr and sideband '3' is used for error
information.
If no 'side-band' capability was specified, the server will stream the
entire packfile without multiplexing.
Pushing Data To a Server
------------------------
Pushing data to a server will invoke the 'receive-pack' process on the
server, which will allow the client to tell it which references it should
update and then send all the data the server will need for those new
references to be complete. Once all the data is received and validated,
the server will then update its references to what the client specified.
Authentication
--------------
The protocol itself contains no authentication mechanisms. That is to be
handled by the transport, such as SSH, before the 'receive-pack' process is
invoked. If 'receive-pack' is configured over the Git transport, those
repositories will be writable by anyone who can access that port (9418) as
that transport is unauthenticated.
Reference Discovery
-------------------
The reference discovery phase is done nearly the same way as it is in the
fetching protocol. Each reference obj-id and name on the server is sent
in packet-line format to the client, followed by a flush-pkt. The only
real difference is that the capability listing is different - the only
possible values are 'report-status', 'report-status-v2', 'delete-refs',
'ofs-delta', 'atomic' and 'push-options'.
Reference Update Request and Packfile Transfer
----------------------------------------------
Once the client knows what references the server is at, it can send a
list of reference update requests. For each reference on the server
that it wants to update, it sends a line listing the obj-id currently on
the server, the obj-id the client would like to update it to and the name
of the reference.
This list is followed by a flush-pkt.
----
update-requests = *shallow ( command-list | push-cert )
shallow = PKT-LINE("shallow" SP obj-id)
command-list = PKT-LINE(command NUL capability-list)
*PKT-LINE(command)
flush-pkt
command = create / delete / update
create = zero-id SP new-id SP name
delete = old-id SP zero-id SP name
update = old-id SP new-id SP name
old-id = obj-id
new-id = obj-id
push-cert = PKT-LINE("push-cert" NUL capability-list LF)
PKT-LINE("certificate version 0.1" LF)
PKT-LINE("pusher" SP ident LF)
PKT-LINE("pushee" SP url LF)
PKT-LINE("nonce" SP nonce LF)
*PKT-LINE("push-option" SP push-option LF)
PKT-LINE(LF)
*PKT-LINE(command LF)
*PKT-LINE(gpg-signature-lines LF)
PKT-LINE("push-cert-end" LF)
push-option = 1*( VCHAR | SP )
----
If the server has advertised the 'push-options' capability and the client has
specified 'push-options' as part of the capability list above, the client then
sends its push options followed by a flush-pkt.
----
push-options = *PKT-LINE(push-option) flush-pkt
----
For backwards compatibility with older Git servers, if the client sends a push
cert and push options, it MUST send its push options both embedded within the
push cert and after the push cert. (Note that the push options within the cert
are prefixed, but the push options after the cert are not.) Both these lists
MUST be the same, modulo the prefix.
After that the packfile that
should contain all the objects that the server will need to complete the new
references will be sent.
----
packfile = "PACK" 28*(OCTET)
----
If the receiving end does not support delete-refs, the sending end MUST
NOT ask for delete command.
If the receiving end does not support push-cert, the sending end
MUST NOT send a push-cert command. When a push-cert command is
sent, command-list MUST NOT be sent; the commands recorded in the
push certificate is used instead.
The packfile MUST NOT be sent if the only command used is 'delete'.
A packfile MUST be sent if either create or update command is used,
even if the server already has all the necessary objects. In this
case the client MUST send an empty packfile. The only time this
is likely to happen is if the client is creating
a new branch or a tag that points to an existing obj-id.
The server will receive the packfile, unpack it, then validate each
reference that is being updated that it hasn't changed while the request
was being processed (the obj-id is still the same as the old-id), and
it will run any update hooks to make sure that the update is acceptable.
If all of that is fine, the server will then update the references.
Push Certificate
----------------
A push certificate begins with a set of header lines. After the
header and an empty line, the protocol commands follow, one per
line. Note that the trailing LF in push-cert PKT-LINEs is _not_
optional; it must be present.
Currently, the following header fields are defined:
`pusher` ident::
Identify the GPG key in "Human Readable Name <email@address>"
format.
`pushee` url::
The repository URL (anonymized, if the URL contains
authentication material) the user who ran `git push`
intended to push into.
`nonce` nonce::
The 'nonce' string the receiving repository asked the
pushing user to include in the certificate, to prevent
replay attacks.
The GPG signature lines are a detached signature for the contents
recorded in the push certificate before the signature block begins.
The detached signature is used to certify that the commands were
given by the pusher, who must be the signer.
Report Status
-------------
After receiving the pack data from the sender, the receiver sends a
report if 'report-status' or 'report-status-v2' capability is in effect.
It is a short listing of what happened in that update. It will first
list the status of the packfile unpacking as either 'unpack ok' or
'unpack [error]'. Then it will list the status for each of the references
that it tried to update. Each line is either 'ok [refname]' if the
update was successful, or 'ng [refname] [error]' if the update was not.
----
report-status = unpack-status
1*(command-status)
flush-pkt
unpack-status = PKT-LINE("unpack" SP unpack-result)
unpack-result = "ok" / error-msg
command-status = command-ok / command-fail
command-ok = PKT-LINE("ok" SP refname)
command-fail = PKT-LINE("ng" SP refname SP error-msg)
error-msg = 1*(OCTET) ; where not "ok"
----
The 'report-status-v2' capability extends the protocol by adding new option
lines in order to support reporting of reference rewritten by the
'proc-receive' hook. The 'proc-receive' hook may handle a command for a
pseudo-reference which may create or update one or more references, and each
reference may have different name, different new-oid, and different old-oid.
----
report-status-v2 = unpack-status
1*(command-status-v2)
flush-pkt
unpack-status = PKT-LINE("unpack" SP unpack-result)
unpack-result = "ok" / error-msg
command-status-v2 = command-ok-v2 / command-fail
command-ok-v2 = command-ok
*option-line
command-ok = PKT-LINE("ok" SP refname)
command-fail = PKT-LINE("ng" SP refname SP error-msg)
error-msg = 1*(OCTET) ; where not "ok"
option-line = *1(option-refname)
*1(option-old-oid)
*1(option-new-oid)
*1(option-forced-update)
option-refname = PKT-LINE("option" SP "refname" SP refname)
option-old-oid = PKT-LINE("option" SP "old-oid" SP obj-id)
option-new-oid = PKT-LINE("option" SP "new-oid" SP obj-id)
option-force = PKT-LINE("option" SP "forced-update")
----
Updates can be unsuccessful for a number of reasons. The reference can have
changed since the reference discovery phase was originally sent, meaning
someone pushed in the meantime. The reference being pushed could be a
non-fast-forward reference and the update hooks or configuration could be
set to not allow that, etc. Also, some references can be updated while others
can be rejected.
An example client/server communication might look like this:
----
S: 006274730d410fcb6603ace96f1dc55ea6196122532d refs/heads/local\0report-status delete-refs ofs-delta\n
S: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe refs/heads/debug\n
S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/master\n
S: 003d74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/team\n
S: 0000
C: 00677d1665144a3a975c05f1f43902ddaf084e784dbe 74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/debug\n
C: 006874730d410fcb6603ace96f1dc55ea6196122532d 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a refs/heads/master\n
C: 0000
C: [PACKDATA]
S: 000eunpack ok\n
S: 0018ok refs/heads/debug\n
S: 002ang refs/heads/master non-fast-forward\n
----

2
Documentation/technical/packfile-uri.txt
View File

@ -18,7 +18,7 @@ a `packfile-uris` argument, the server MAY send a `packfile-uris` section
directly before the `packfile` section (right after `wanted-refs` if it is
sent) containing URIs of any of the given protocols. The URIs point to
packfiles that use only features that the client has declared that it supports
(e.g. ofs-delta and thin-pack). See protocol-v2.txt for the documentation of
(e.g. ofs-delta and thin-pack). See linkgit:gitprotocol-v2[5] for the documentation of
this section.
Clients should then download and index all the given URIs (in addition to

2
Documentation/technical/partial-clone.txt
View File

@ -79,7 +79,7 @@ Design Details
upload-pack negotiation.
+
This uses the existing capability discovery mechanism.
See "filter" in Documentation/technical/pack-protocol.txt.
See "filter" in linkgit:gitprotocol-pack[5].
- Clients pass a "filter-spec" to clone and fetch which is passed to the
server to request filtering during packfile construction.

380
Documentation/technical/protocol-capabilities.txt
View File

@ -1,380 +0,0 @@
Git Protocol Capabilities
=========================
NOTE: this document describes capabilities for versions 0 and 1 of the pack
protocol. For version 2, please refer to the link:protocol-v2.html[protocol-v2]
doc.
Servers SHOULD support all capabilities defined in this document.
On the very first line of the initial server response of either
receive-pack and upload-pack the first reference is followed by
a NUL byte and then a list of space delimited server capabilities.
These allow the server to declare what it can and cannot support
to the client.
Client will then send a space separated list of capabilities it wants
to be in effect. The client MUST NOT ask for capabilities the server
did not say it supports.
Server MUST diagnose and abort if capabilities it does not understand
was sent. Server MUST NOT ignore capabilities that client requested
and server advertised. As a consequence of these rules, server MUST
NOT advertise capabilities it does not understand.
The 'atomic', 'report-status', 'report-status-v2', 'delete-refs', 'quiet',
and 'push-cert' capabilities are sent and recognized by the receive-pack
(push to server) process.
The 'ofs-delta' and 'side-band-64k' capabilities are sent and recognized
by both upload-pack and receive-pack protocols. The 'agent' and 'session-id'
capabilities may optionally be sent in both protocols.
All other capabilities are only recognized by the upload-pack (fetch
from server) process.
multi_ack
---------
The 'multi_ack' capability allows the server to return "ACK obj-id
continue" as soon as it finds a commit that it can use as a common
base, between the client's wants and the client's have set.
By sending this early, the server can potentially head off the client
from walking any further down that particular branch of the client's
repository history. The client may still need to walk down other
branches, sending have lines for those, until the server has a
complete cut across the DAG, or the client has said "done".
Without multi_ack, a client sends have lines in --date-order until
the server has found a common base. That means the client will send
have lines that are already known by the server to be common, because
they overlap in time with another branch that the server hasn't found
a common base on yet.
For example suppose the client has commits in caps that the server
doesn't and the server has commits in lower case that the client
doesn't, as in the following diagram:
+---- u ---------------------- x
/ +----- y
/ /
a -- b -- c -- d -- E -- F
\
+--- Q -- R -- S
If the client wants x,y and starts out by saying have F,S, the server
doesn't know what F,S is. Eventually the client says "have d" and
the server sends "ACK d continue" to let the client know to stop
walking down that line (so don't send c-b-a), but it's not done yet,
it needs a base for x. The client keeps going with S-R-Q, until a
gets reached, at which point the server has a clear base and it all
ends.
Without multi_ack the client would have sent that c-b-a chain anyway,
interleaved with S-R-Q.
multi_ack_detailed
------------------
This is an extension of multi_ack that permits client to better
understand the server's in-memory state. See pack-protocol.txt,
section "Packfile Negotiation" for more information.
no-done
-------
This capability should only be used with the smart HTTP protocol. If
multi_ack_detailed and no-done are both present, then the sender is
free to immediately send a pack following its first "ACK obj-id ready"
message.
Without no-done in the smart HTTP protocol, the server session would
end and the client has to make another trip to send "done" before
the server can send the pack. no-done removes the last round and
thus slightly reduces latency.
thin-pack
---------
A thin pack is one with deltas which reference base objects not
contained within the pack (but are known to exist at the receiving
end). This can reduce the network traffic significantly, but it
requires the receiving end to know how to "thicken" these packs by
adding the missing bases to the pack.
The upload-pack server advertises 'thin-pack' when it can generate
and send a thin pack. A client requests the 'thin-pack' capability
when it understands how to "thicken" it, notifying the server that
it can receive such a pack. A client MUST NOT request the
'thin-pack' capability if it cannot turn a thin pack into a
self-contained pack.
Receive-pack, on the other hand, is assumed by default to be able to
handle thin packs, but can ask the client not to use the feature by
advertising the 'no-thin' capability. A client MUST NOT send a thin
pack if the server advertises the 'no-thin' capability.
The reasons for this asymmetry are historical. The receive-pack
program did not exist until after the invention of thin packs, so
historically the reference implementation of receive-pack always
understood thin packs. Adding 'no-thin' later allowed receive-pack
to disable the feature in a backwards-compatible manner.
side-band, side-band-64k
------------------------
This capability means that server can send, and client understand multiplexed
progress reports and error info interleaved with the packfile itself.
These two options are mutually exclusive. A modern client always
favors 'side-band-64k'.
Either mode indicates that the packfile data will be streamed broken
up into packets of up to either 1000 bytes in the case of 'side_band',
or 65520 bytes in the case of 'side_band_64k'. Each packet is made up
of a leading 4-byte pkt-line length of how much data is in the packet,
followed by a 1-byte stream code, followed by the actual data.
The stream code can be one of:
1 - pack data
2 - progress messages
3 - fatal error message just before stream aborts
The "side-band-64k" capability came about as a way for newer clients
that can handle much larger packets to request packets that are
actually crammed nearly full, while maintaining backward compatibility
for the older clients.
Further, with side-band and its up to 1000-byte messages, it's actually
999 bytes of payload and 1 byte for the stream code. With side-band-64k,
same deal, you have up to 65519 bytes of data and 1 byte for the stream
code.
The client MUST send only maximum of one of "side-band" and "side-
band-64k". Server MUST diagnose it as an error if client requests
both.
ofs-delta
---------
Server can send, and client understand PACKv2 with delta referring to
its base by position in pack rather than by an obj-id. That is, they can
send/read OBJ_OFS_DELTA (aka type 6) in a packfile.
agent
-----
The server may optionally send a capability of the form `agent=X` to
notify the client that the server is running version `X`. The client may
optionally return its own agent string by responding with an `agent=Y`
capability (but it MUST NOT do so if the server did not mention the
agent capability). The `X` and `Y` strings may contain any printable
ASCII characters except space (i.e., the byte range 32 < x < 127), and
are typically of the form "package/version" (e.g., "git/1.8.3.1"). The
agent strings are purely informative for statistics and debugging
purposes, and MUST NOT be used to programmatically assume the presence
or absence of particular features.
object-format
-------------
This capability, which takes a hash algorithm as an argument, indicates
that the server supports the given hash algorithms. It may be sent
multiple times; if so, the first one given is the one used in the ref
advertisement.
When provided by the client, this indicates that it intends to use the
given hash algorithm to communicate. The algorithm provided must be one
that the server supports.
If this capability is not provided, it is assumed that the only
supported algorithm is SHA-1.
symref
------
This parameterized capability is used to inform the receiver which symbolic ref
points to which ref; for example, "symref=HEAD:refs/heads/master" tells the
receiver that HEAD points to master. This capability can be repeated to
represent multiple symrefs.
Servers SHOULD include this capability for the HEAD symref if it is one of the
refs being sent.
Clients MAY use the parameters from this capability to select the proper initial
branch when cloning a repository.
shallow
-------
This capability adds "deepen", "shallow" and "unshallow" commands to
the fetch-pack/upload-pack protocol so clients can request shallow
clones.
deepen-since
------------
This capability adds "deepen-since" command to fetch-pack/upload-pack
protocol so the client can request shallow clones that are cut at a
specific time, instead of depth. Internally it's equivalent of doing
"rev-list --max-age=<timestamp>" on the server side. "deepen-since"
cannot be used with "deepen".
deepen-not
----------
This capability adds "deepen-not" command to fetch-pack/upload-pack
protocol so the client can request shallow clones that are cut at a
specific revision, instead of depth. Internally it's equivalent of
doing "rev-list --not <rev>" on the server side. "deepen-not"
cannot be used with "deepen", but can be used with "deepen-since".
deepen-relative
---------------
If this capability is requested by the client, the semantics of
"deepen" command is changed. The "depth" argument is the depth from
the current shallow boundary, instead of the depth from remote refs.
no-progress
-----------
The client was started with "git clone -q" or something, and doesn't
want that side band 2. Basically the client just says "I do not
wish to receive stream 2 on sideband, so do not send it to me, and if
you did, I will drop it on the floor anyway". However, the sideband
channel 3 is still used for error responses.
include-tag
-----------
The 'include-tag' capability is about sending annotated tags if we are
sending objects they point to. If we pack an object to the client, and
a tag object points exactly at that object, we pack the tag object too.
In general this allows a client to get all new annotated tags when it
fetches a branch, in a single network connection.
Clients MAY always send include-tag, hardcoding it into a request when
the server advertises this capability. The decision for a client to
request include-tag only has to do with the client's desires for tag
data, whether or not a server had advertised objects in the
refs/tags/* namespace.
Servers MUST pack the tags if their referrant is packed and the client
has requested include-tags.
Clients MUST be prepared for the case where a server has ignored
include-tag and has not actually sent tags in the pack. In such
cases the client SHOULD issue a subsequent fetch to acquire the tags
that include-tag would have otherwise given the client.
The server SHOULD send include-tag, if it supports it, regardless
of whether or not there are tags available.
report-status
-------------
The receive-pack process can receive a 'report-status' capability,
which tells it that the client wants a report of what happened after
a packfile upload and reference update. If the pushing client requests
this capability, after unpacking and updating references the server
will respond with whether the packfile unpacked successfully and if
each reference was updated successfully. If any of those were not
successful, it will send back an error message. See pack-protocol.txt
for example messages.
report-status-v2
----------------
Capability 'report-status-v2' extends capability 'report-status' by
adding new "option" directives in order to support reference rewritten by
the "proc-receive" hook. The "proc-receive" hook may handle a command
for a pseudo-reference which may create or update a reference with
different name, new-oid, and old-oid. While the capability
'report-status' cannot report for such case. See pack-protocol.txt
for details.
delete-refs
-----------
If the server sends back the 'delete-refs' capability, it means that
it is capable of accepting a zero-id value as the target
value of a reference update. It is not sent back by the client, it
simply informs the client that it can be sent zero-id values
to delete references.
quiet
-----
If the receive-pack server advertises the 'quiet' capability, it is
capable of silencing human-readable progress output which otherwise may
be shown when processing the received pack. A send-pack client should
respond with the 'quiet' capability to suppress server-side progress
reporting if the local progress reporting is also being suppressed
(e.g., via `push -q`, or if stderr does not go to a tty).
atomic
------
If the server sends the 'atomic' capability it is capable of accepting
atomic pushes. If the pushing client requests this capability, the server
will update the refs in one atomic transaction. Either all refs are
updated or none.
push-options
------------
If the server sends the 'push-options' capability it is able to accept
push options after the update commands have been sent, but before the
packfile is streamed. If the pushing client requests this capability,
the server will pass the options to the pre- and post- receive hooks
that process this push request.
allow-tip-sha1-in-want
----------------------
If the upload-pack server advertises this capability, fetch-pack may
send "want" lines with object names that exist at the server but are not
advertised by upload-pack. For historical reasons, the name of this
capability contains "sha1". Object names are always given using the
object format negotiated through the 'object-format' capability.
allow-reachable-sha1-in-want
----------------------------
If the upload-pack server advertises this capability, fetch-pack may
send "want" lines with object names that exist at the server but are not
advertised by upload-pack. For historical reasons, the name of this
capability contains "sha1". Object names are always given using the
object format negotiated through the 'object-format' capability.
push-cert=<nonce>
-----------------
The receive-pack server that advertises this capability is willing
to accept a signed push certificate, and asks the <nonce> to be
included in the push certificate. A send-pack client MUST NOT
send a push-cert packet unless the receive-pack server advertises
this capability.
filter
------
If the upload-pack server advertises the 'filter' capability,
fetch-pack may send "filter" commands to request a partial clone
or partial fetch and request that the server omit various objects
from the packfile.
session-id=<session id>
-----------------------
The server may advertise a session ID that can be used to identify this process
across multiple requests. The client may advertise its own session ID back to
the server as well.
Session IDs should be unique to a given process. They must fit within a
packet-line, and must not contain non-printable or whitespace characters. The
current implementation uses trace2 session IDs (see
link:api-trace2.html[api-trace2] for details), but this may change and users of
the session ID should not rely on this fact.

99
Documentation/technical/protocol-common.txt
View File

@ -1,99 +0,0 @@
Documentation Common to Pack and Http Protocols
===============================================
ABNF Notation
-------------
ABNF notation as described by RFC 5234 is used within the protocol documents,
except the following replacement core rules are used:
----
HEXDIG = DIGIT / "a" / "b" / "c" / "d" / "e" / "f"
----
We also define the following common rules:
----
NUL = %x00
zero-id = 40*"0"
obj-id = 40*(HEXDIGIT)
refname = "HEAD"
refname /= "refs/" <see discussion below>
----
A refname is a hierarchical octet string beginning with "refs/" and
not violating the 'git-check-ref-format' command's validation rules.
More specifically, they:
. They can include slash `/` for hierarchical (directory)
grouping, but no slash-separated component can begin with a
dot `.`.
. They must contain at least one `/`. This enforces the presence of a
category like `heads/`, `tags/` etc. but the actual names are not
restricted.
. They cannot have two consecutive dots `..` anywhere.
. They cannot have ASCII control characters (i.e. bytes whose
values are lower than \040, or \177 `DEL`), space, tilde `~`,
caret `^`, colon `:`, question-mark `?`, asterisk `*`,
or open bracket `[` anywhere.
. They cannot end with a slash `/` or a dot `.`.
. They cannot end with the sequence `.lock`.
. They cannot contain a sequence `@{`.
. They cannot contain a `\\`.
pkt-line Format
---------------
Much (but not all) of the payload is described around pkt-lines.
A pkt-line is a variable length binary string. The first four bytes
of the line, the pkt-len, indicates the total length of the line,
in hexadecimal. The pkt-len includes the 4 bytes used to contain
the length's hexadecimal representation.
A pkt-line MAY contain binary data, so implementors MUST ensure
pkt-line parsing/formatting routines are 8-bit clean.
A non-binary line SHOULD BE terminated by an LF, which if present
MUST be included in the total length. Receivers MUST treat pkt-lines
with non-binary data the same whether or not they contain the trailing
LF (stripping the LF if present, and not complaining when it is
missing).
The maximum length of a pkt-line's data component is 65516 bytes.
Implementations MUST NOT send pkt-line whose length exceeds 65520
(65516 bytes of payload + 4 bytes of length data).
Implementations SHOULD NOT send an empty pkt-line ("0004").
A pkt-line with a length field of 0 ("0000"), called a flush-pkt,
is a special case and MUST be handled differently than an empty
pkt-line ("0004").
----
pkt-line = data-pkt / flush-pkt
data-pkt = pkt-len pkt-payload
pkt-len = 4*(HEXDIG)
pkt-payload = (pkt-len - 4)*(OCTET)
flush-pkt = "0000"
----
Examples (as C-style strings):
----
pkt-line actual value
---------------------------------
"0006a\n" "a\n"
"0005a" "a"
"000bfoobar\n" "foobar\n"
"0004" ""
----

568
Documentation/technical/protocol-v2.txt
View File

@ -1,568 +0,0 @@
Git Wire Protocol, Version 2
============================
This document presents a specification for a version 2 of Git's wire
protocol. Protocol v2 will improve upon v1 in the following ways:
* Instead of multiple service names, multiple commands will be
supported by a single service
* Easily extendable as capabilities are moved into their own section
of the protocol, no longer being hidden behind a NUL byte and
limited by the size of a pkt-line
* Separate out other information hidden behind NUL bytes (e.g. agent
string as a capability and symrefs can be requested using 'ls-refs')
* Reference advertisement will be omitted unless explicitly requested
* ls-refs command to explicitly request some refs
* Designed with http and stateless-rpc in mind. With clear flush
semantics the http remote helper can simply act as a proxy
In protocol v2 communication is command oriented. When first contacting a
server a list of capabilities will advertised. Some of these capabilities
will be commands which a client can request be executed. Once a command
has completed, a client can reuse the connection and request that other
commands be executed.
Packet-Line Framing
-------------------
All communication is done using packet-line framing, just as in v1. See
`Documentation/technical/pack-protocol.txt` and
`Documentation/technical/protocol-common.txt` for more information.
In protocol v2 these special packets will have the following semantics:
* '0000' Flush Packet (flush-pkt) - indicates the end of a message
* '0001' Delimiter Packet (delim-pkt) - separates sections of a message
* '0002' Response End Packet (response-end-pkt) - indicates the end of a
response for stateless connections
Initial Client Request
----------------------
In general a client can request to speak protocol v2 by sending
`version=2` through the respective side-channel for the transport being
used which inevitably sets `GIT_PROTOCOL`. More information can be
found in `pack-protocol.txt` and `http-protocol.txt`, as well as the
`GIT_PROTOCOL` definition in `git.txt`. In all cases the
response from the server is the capability advertisement.
Git Transport
~~~~~~~~~~~~~
When using the git:// transport, you can request to use protocol v2 by
sending "version=2" as an extra parameter:
003egit-upload-pack /project.git\0host=myserver.com\0\0version=2\0
SSH and File Transport
~~~~~~~~~~~~~~~~~~~~~~
When using either the ssh:// or file:// transport, the GIT_PROTOCOL
environment variable must be set explicitly to include "version=2".
The server may need to be configured to allow this environment variable
to pass.
HTTP Transport
~~~~~~~~~~~~~~
When using the http:// or https:// transport a client makes a "smart"
info/refs request as described in `http-protocol.txt` and requests that
v2 be used by supplying "version=2" in the `Git-Protocol` header.
C: GET $GIT_URL/info/refs?service=git-upload-pack HTTP/1.0
C: Git-Protocol: version=2
A v2 server would reply:
S: 200 OK
S: <Some headers>
S: ...
S:
S: 000eversion 2\n
S: <capability-advertisement>
Subsequent requests are then made directly to the service
`$GIT_URL/git-upload-pack`. (This works the same for git-receive-pack).
Uses the `--http-backend-info-refs` option to
linkgit:git-upload-pack[1].
The server may need to be configured to pass this header's contents via
the `GIT_PROTOCOL` variable. See the discussion in `git-http-backend.txt`.
Capability Advertisement
------------------------
A server which decides to communicate (based on a request from a client)
using protocol version 2, notifies the client by sending a version string
in its initial response followed by an advertisement of its capabilities.
Each capability is a key with an optional value. Clients must ignore all
unknown keys. Semantics of unknown values are left to the definition of
each key. Some capabilities will describe commands which can be requested
to be executed by the client.
capability-advertisement = protocol-version
capability-list
flush-pkt
protocol-version = PKT-LINE("version 2" LF)
capability-list = *capability
capability = PKT-LINE(key[=value] LF)
key = 1*(ALPHA | DIGIT | "-_")
value = 1*(ALPHA | DIGIT | " -_.,?\/{}[]()<>!@#$%^&*+=:;")
Command Request
---------------
After receiving the capability advertisement, a client can then issue a
request to select the command it wants with any particular capabilities
or arguments. There is then an optional section where the client can
provide any command specific parameters or queries. Only a single
command can be requested at a time.
request = empty-request | command-request
empty-request = flush-pkt
command-request = command
capability-list
delim-pkt
command-args
flush-pkt
command = PKT-LINE("command=" key LF)
command-args = *command-specific-arg
command-specific-args are packet line framed arguments defined by
each individual command.
The server will then check to ensure that the client's request is
comprised of a valid command as well as valid capabilities which were
advertised. If the request is valid the server will then execute the
command. A server MUST wait till it has received the client's entire
request before issuing a response. The format of the response is
determined by the command being executed, but in all cases a flush-pkt
indicates the end of the response.
When a command has finished, and the client has received the entire
response from the server, a client can either request that another
command be executed or can terminate the connection. A client may
optionally send an empty request consisting of just a flush-pkt to
indicate that no more requests will be made.
Capabilities
------------
There are two different types of capabilities: normal capabilities,
which can be used to convey information or alter the behavior of a
request, and commands, which are the core actions that a client wants to
perform (fetch, push, etc).
Protocol version 2 is stateless by default. This means that all commands
must only last a single round and be stateless from the perspective of the
server side, unless the client has requested a capability indicating that
state should be maintained by the server. Clients MUST NOT require state
management on the server side in order to function correctly. This
permits simple round-robin load-balancing on the server side, without
needing to worry about state management.
agent
~~~~~
The server can advertise the `agent` capability with a value `X` (in the
form `agent=X`) to notify the client that the server is running version
`X`. The client may optionally send its own agent string by including
the `agent` capability with a value `Y` (in the form `agent=Y`) in its
request to the server (but it MUST NOT do so if the server did not
advertise the agent capability). The `X` and `Y` strings may contain any
printable ASCII characters except space (i.e., the byte range 32 < x <
127), and are typically of the form "package/version" (e.g.,
"git/1.8.3.1"). The agent strings are purely informative for statistics
and debugging purposes, and MUST NOT be used to programmatically assume
the presence or absence of particular features.
ls-refs
~~~~~~~
`ls-refs` is the command used to request a reference advertisement in v2.
Unlike the current reference advertisement, ls-refs takes in arguments
which can be used to limit the refs sent from the server.
Additional features not supported in the base command will be advertised
as the value of the command in the capability advertisement in the form
of a space separated list of features: "<command>=<feature 1> <feature 2>"
ls-refs takes in the following arguments:
symrefs
In addition to the object pointed by it, show the underlying ref
pointed by it when showing a symbolic ref.
peel
Show peeled tags.
ref-prefix <prefix>
When specified, only references having a prefix matching one of
the provided prefixes are displayed. Multiple instances may be
given, in which case references matching any prefix will be
shown. Note that this is purely for optimization; a server MAY
show refs not matching the prefix if it chooses, and clients
should filter the result themselves.
If the 'unborn' feature is advertised the following argument can be
included in the client's request.
unborn
The server will send information about HEAD even if it is a symref
pointing to an unborn branch in the form "unborn HEAD
symref-target:<target>".
The output of ls-refs is as follows:
output = *ref
flush-pkt
obj-id-or-unborn = (obj-id | "unborn")
ref = PKT-LINE(obj-id-or-unborn SP refname *(SP ref-attribute) LF)
ref-attribute = (symref | peeled)
symref = "symref-target:" symref-target
peeled = "peeled:" obj-id
fetch
~~~~~
`fetch` is the command used to fetch a packfile in v2. It can be looked
at as a modified version of the v1 fetch where the ref-advertisement is
stripped out (since the `ls-refs` command fills that role) and the
message format is tweaked to eliminate redundancies and permit easy
addition of future extensions.
Additional features not supported in the base command will be advertised
as the value of the command in the capability advertisement in the form
of a space separated list of features: "<command>=<feature 1> <feature 2>"
A `fetch` request can take the following arguments:
want <oid>
Indicates to the server an object which the client wants to
retrieve. Wants can be anything and are not limited to
advertised objects.
have <oid>
Indicates to the server an object which the client has locally.
This allows the server to make a packfile which only contains
the objects that the client needs. Multiple 'have' lines can be
supplied.
done
Indicates to the server that negotiation should terminate (or
not even begin if performing a clone) and that the server should
use the information supplied in the request to construct the
packfile.
thin-pack
Request that a thin pack be sent, which is a pack with deltas
which reference base objects not contained within the pack (but
are known to exist at the receiving end). This can reduce the
network traffic significantly, but it requires the receiving end
to know how to "thicken" these packs by adding the missing bases
to the pack.
no-progress
Request that progress information that would normally be sent on
side-band channel 2, during the packfile transfer, should not be
sent. However, the side-band channel 3 is still used for error
responses.
include-tag
Request that annotated tags should be sent if the objects they
point to are being sent.
ofs-delta
Indicate that the client understands PACKv2 with delta referring
to its base by position in pack rather than by an oid. That is,
they can read OBJ_OFS_DELTA (aka type 6) in a packfile.
If the 'shallow' feature is advertised the following arguments can be
included in the clients request as well as the potential addition of the
'shallow-info' section in the server's response as explained below.
shallow <oid>
A client must notify the server of all commits for which it only
has shallow copies (meaning that it doesn't have the parents of
a commit) by supplying a 'shallow <oid>' line for each such
object so that the server is aware of the limitations of the
client's history. This is so that the server is aware that the
client may not have all objects reachable from such commits.
deepen <depth>
Requests that the fetch/clone should be shallow having a commit
depth of <depth> relative to the remote side.
deepen-relative
Requests that the semantics of the "deepen" command be changed
to indicate that the depth requested is relative to the client's
current shallow boundary, instead of relative to the requested
commits.
deepen-since <timestamp>
Requests that the shallow clone/fetch should be cut at a
specific time, instead of depth. Internally it's equivalent to
doing "git rev-list --max-age=<timestamp>". Cannot be used with
"deepen".
deepen-not <rev>
Requests that the shallow clone/fetch should be cut at a
specific revision specified by '<rev>', instead of a depth.
Internally it's equivalent of doing "git rev-list --not <rev>".
Cannot be used with "deepen", but can be used with
"deepen-since".
If the 'filter' feature is advertised, the following argument can be
included in the client's request:
filter <filter-spec>
Request that various objects from the packfile be omitted
using one of several filtering techniques. These are intended
for use with partial clone and partial fetch operations. See
`rev-list` for possible "filter-spec" values. When communicating
with other processes, senders SHOULD translate scaled integers
(e.g. "1k") into a fully-expanded form (e.g. "1024") to aid
interoperability with older receivers that may not understand
newly-invented scaling suffixes. However, receivers SHOULD
accept the following suffixes: 'k', 'm', and 'g' for 1024,
1048576, and 1073741824, respectively.
If the 'ref-in-want' feature is advertised, the following argument can
be included in the client's request as well as the potential addition of
the 'wanted-refs' section in the server's response as explained below.
want-ref <ref>
Indicates to the server that the client wants to retrieve a
particular ref, where <ref> is the full name of a ref on the
server.
If the 'sideband-all' feature is advertised, the following argument can be
included in the client's request:
sideband-all
Instruct the server to send the whole response multiplexed, not just
the packfile section. All non-flush and non-delim PKT-LINE in the
response (not only in the packfile section) will then start with a byte
indicating its sideband (1, 2, or 3), and the server may send "0005\2"
(a PKT-LINE of sideband 2 with no payload) as a keepalive packet.
If the 'packfile-uris' feature is advertised, the following argument
can be included in the client's request as well as the potential
addition of the 'packfile-uris' section in the server's response as
explained below.
packfile-uris <comma-separated list of protocols>
Indicates to the server that the client is willing to receive
URIs of any of the given protocols in place of objects in the
sent packfile. Before performing the connectivity check, the
client should download from all given URIs. Currently, the
protocols supported are "http" and "https".
If the 'wait-for-done' feature is advertised, the following argument
can be included in the client's request.
wait-for-done
Indicates to the server that it should never send "ready", but
should wait for the client to say "done" before sending the
packfile.
The response of `fetch` is broken into a number of sections separated by
delimiter packets (0001), with each section beginning with its section
header. Most sections are sent only when the packfile is sent.
output = acknowledgements flush-pkt |
[acknowledgments delim-pkt] [shallow-info delim-pkt]
[wanted-refs delim-pkt] [packfile-uris delim-pkt]
packfile flush-pkt
acknowledgments = PKT-LINE("acknowledgments" LF)
(nak | *ack)
(ready)
ready = PKT-LINE("ready" LF)
nak = PKT-LINE("NAK" LF)
ack = PKT-LINE("ACK" SP obj-id LF)
shallow-info = PKT-LINE("shallow-info" LF)
*PKT-LINE((shallow | unshallow) LF)
shallow = "shallow" SP obj-id
unshallow = "unshallow" SP obj-id
wanted-refs = PKT-LINE("wanted-refs" LF)
*PKT-LINE(wanted-ref LF)
wanted-ref = obj-id SP refname
packfile-uris = PKT-LINE("packfile-uris" LF) *packfile-uri
packfile-uri = PKT-LINE(40*(HEXDIGIT) SP *%x20-ff LF)
packfile = PKT-LINE("packfile" LF)
*PKT-LINE(%x01-03 *%x00-ff)
acknowledgments section
* If the client determines that it is finished with negotiations by
sending a "done" line (thus requiring the server to send a packfile),
the acknowledgments sections MUST be omitted from the server's
response.
* Always begins with the section header "acknowledgments"
* The server will respond with "NAK" if none of the object ids sent
as have lines were common.
* The server will respond with "ACK obj-id" for all of the
object ids sent as have lines which are common.
* A response cannot have both "ACK" lines as well as a "NAK"
line.
* The server will respond with a "ready" line indicating that
the server has found an acceptable common base and is ready to
make and send a packfile (which will be found in the packfile
section of the same response)
* If the server has found a suitable cut point and has decided
to send a "ready" line, then the server can decide to (as an
optimization) omit any "ACK" lines it would have sent during
its response. This is because the server will have already
determined the objects it plans to send to the client and no
further negotiation is needed.
shallow-info section
* If the client has requested a shallow fetch/clone, a shallow
client requests a fetch or the server is shallow then the
server's response may include a shallow-info section. The
shallow-info section will be included if (due to one of the
above conditions) the server needs to inform the client of any
shallow boundaries or adjustments to the clients already
existing shallow boundaries.
* Always begins with the section header "shallow-info"
* If a positive depth is requested, the server will compute the
set of commits which are no deeper than the desired depth.
* The server sends a "shallow obj-id" line for each commit whose
parents will not be sent in the following packfile.
* The server sends an "unshallow obj-id" line for each commit
which the client has indicated is shallow, but is no longer
shallow as a result of the fetch (due to its parents being
sent in the following packfile).
* The server MUST NOT send any "unshallow" lines for anything
which the client has not indicated was shallow as a part of
its request.
wanted-refs section
* This section is only included if the client has requested a
ref using a 'want-ref' line and if a packfile section is also
included in the response.
* Always begins with the section header "wanted-refs".
* The server will send a ref listing ("<oid> <refname>") for
each reference requested using 'want-ref' lines.
* The server MUST NOT send any refs which were not requested
using 'want-ref' lines.
packfile-uris section
* This section is only included if the client sent
'packfile-uris' and the server has at least one such URI to
send.
* Always begins with the section header "packfile-uris".
* For each URI the server sends, it sends a hash of the pack's
contents (as output by git index-pack) followed by the URI.
* The hashes are 40 hex characters long. When Git upgrades to a new
hash algorithm, this might need to be updated. (It should match
whatever index-pack outputs after "pack\t" or "keep\t".
packfile section
* This section is only included if the client has sent 'want'
lines in its request and either requested that no more
negotiation be done by sending 'done' or if the server has
decided it has found a sufficient cut point to produce a
packfile.
* Always begins with the section header "packfile"
* The transmission of the packfile begins immediately after the
section header
* The data transfer of the packfile is always multiplexed, using
the same semantics of the 'side-band-64k' capability from
protocol version 1. This means that each packet, during the
packfile data stream, is made up of a leading 4-byte pkt-line
length (typical of the pkt-line format), followed by a 1-byte
stream code, followed by the actual data.
The stream code can be one of:
1 - pack data
2 - progress messages
3 - fatal error message just before stream aborts
server-option
~~~~~~~~~~~~~
If advertised, indicates that any number of server specific options can be
included in a request. This is done by sending each option as a
"server-option=<option>" capability line in the capability-list section of
a request.
The provided options must not contain a NUL or LF character.
object-format
~~~~~~~~~~~~~~~
The server can advertise the `object-format` capability with a value `X` (in the
form `object-format=X`) to notify the client that the server is able to deal
with objects using hash algorithm X. If not specified, the server is assumed to
only handle SHA-1. If the client would like to use a hash algorithm other than
SHA-1, it should specify its object-format string.
session-id=<session id>
~~~~~~~~~~~~~~~~~~~~~~~
The server may advertise a session ID that can be used to identify this process
across multiple requests. The client may advertise its own session ID back to
the server as well.
Session IDs should be unique to a given process. They must fit within a
packet-line, and must not contain non-printable or whitespace characters. The
current implementation uses trace2 session IDs (see
link:api-trace2.html[api-trace2] for details), but this may change and users of
the session ID should not rely on this fact.
object-info
~~~~~~~~~~~
`object-info` is the command to retrieve information about one or more objects.
Its main purpose is to allow a client to make decisions based on this
information without having to fully fetch objects. Object size is the only
information that is currently supported.
An `object-info` request takes the following arguments:
size
Requests size information to be returned for each listed object id.
oid <oid>
Indicates to the server an object which the client wants to obtain
information for.
The response of `object-info` is a list of the requested object ids
and associated requested information, each separated by a single space.
output = info flush-pkt
info = PKT-LINE(attrs) LF)
*PKT-LINE(obj-info LF)
attrs = attr | attrs SP attrs
attr = "size"
obj-info = obj-id SP obj-size