git@vger.kernel.org list mirror (unofficial, one of many)
 help / color / mirror / code / Atom feed
73d4ee7f2745610195f1462b2a55ab0c448c433f blob 14893 bytes (raw)

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
 
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 'trace2-sid'
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.

trace2-sid=<session-id>
-----------------------

If trace2 tracing is enabled on the server, it may advertise its session ID via
this capability. The client may choose to log the server's session ID in its
trace logs, and advertise its own session ID back to the server for it to log
as well. This allows for easier debugging of remote sessions when both client
and server logs are available.
debug log:

solving 73d4ee7f27 ...
found 73d4ee7f27 in https://public-inbox.org/git/d04028c3c7574e3ca0f9c1b3d711192ca756158d.1604006121.git.steadmon@google.com/ ||
	https://public-inbox.org/git/d04028c3c7574e3ca0f9c1b3d711192ca756158d.1604355792.git.steadmon@google.com/
found ba869a7d36 in git.git.git
preparing index
index prepared:
100644 ba869a7d366aa1dc13291fb28a2b6bf93b5f5e54	Documentation/technical/protocol-capabilities.txt

applying [1/2] https://public-inbox.org/git/d04028c3c7574e3ca0f9c1b3d711192ca756158d.1604006121.git.steadmon@google.com/
diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt
index ba869a7d36..73d4ee7f27 100644

Checking patch Documentation/technical/protocol-capabilities.txt...
Applied patch Documentation/technical/protocol-capabilities.txt cleanly.

skipping https://public-inbox.org/git/d04028c3c7574e3ca0f9c1b3d711192ca756158d.1604355792.git.steadmon@google.com/ for 73d4ee7f27
index at:
100644 73d4ee7f2745610195f1462b2a55ab0c448c433f	Documentation/technical/protocol-capabilities.txt

Code repositories for project(s) associated with this inbox:

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).