Merge branch 'so/glossary-ancestor'
[git/git.git] / Documentation / gitremote-helpers.txt
1 gitremote-helpers(1)
2 ====================
3
4 NAME
5 ----
6 gitremote-helpers - Helper programs to interact with remote repositories
7
8 SYNOPSIS
9 --------
10 [verse]
11 'git remote-<transport>' <repository> [<URL>]
12
13 DESCRIPTION
14 -----------
15
16 Remote helper programs are normally not used directly by end users,
17 but they are invoked by Git when it needs to interact with remote
18 repositories Git does not support natively. A given helper will
19 implement a subset of the capabilities documented here. When Git
20 needs to interact with a repository using a remote helper, it spawns
21 the helper as an independent process, sends commands to the helper's
22 standard input, and expects results from the helper's standard
23 output. Because a remote helper runs as an independent process from
24 Git, there is no need to re-link Git to add a new helper, nor any
25 need to link the helper with the implementation of Git.
26
27 Every helper must support the "capabilities" command, which Git
28 uses to determine what other commands the helper will accept. Those
29 other commands can be used to discover and update remote refs,
30 transport objects between the object database and the remote repository,
31 and update the local object store.
32
33 Git comes with a "curl" family of remote helpers, that handle various
34 transport protocols, such as 'git-remote-http', 'git-remote-https',
35 'git-remote-ftp' and 'git-remote-ftps'. They implement the capabilities
36 'fetch', 'option', and 'push'.
37
38 INVOCATION
39 ----------
40
41 Remote helper programs are invoked with one or (optionally) two
42 arguments. The first argument specifies a remote repository as in Git;
43 it is either the name of a configured remote or a URL. The second
44 argument specifies a URL; it is usually of the form
45 '<transport>://<address>', but any arbitrary string is possible.
46 The `GIT_DIR` environment variable is set up for the remote helper
47 and can be used to determine where to store additional data or from
48 which directory to invoke auxiliary Git commands.
49
50 When Git encounters a URL of the form '<transport>://<address>', where
51 '<transport>' is a protocol that it cannot handle natively, it
52 automatically invokes 'git remote-<transport>' with the full URL as
53 the second argument. If such a URL is encountered directly on the
54 command line, the first argument is the same as the second, and if it
55 is encountered in a configured remote, the first argument is the name
56 of that remote.
57
58 A URL of the form '<transport>::<address>' explicitly instructs Git to
59 invoke 'git remote-<transport>' with '<address>' as the second
60 argument. If such a URL is encountered directly on the command line,
61 the first argument is '<address>', and if it is encountered in a
62 configured remote, the first argument is the name of that remote.
63
64 Additionally, when a configured remote has `remote.<name>.vcs` set to
65 '<transport>', Git explicitly invokes 'git remote-<transport>' with
66 '<name>' as the first argument. If set, the second argument is
67 `remote.<name>.url`; otherwise, the second argument is omitted.
68
69 INPUT FORMAT
70 ------------
71
72 Git sends the remote helper a list of commands on standard input, one
73 per line. The first command is always the 'capabilities' command, in
74 response to which the remote helper must print a list of the
75 capabilities it supports (see below) followed by a blank line. The
76 response to the capabilities command determines what commands Git uses
77 in the remainder of the command stream.
78
79 The command stream is terminated by a blank line. In some cases
80 (indicated in the documentation of the relevant commands), this blank
81 line is followed by a payload in some other protocol (e.g., the pack
82 protocol), while in others it indicates the end of input.
83
84 Capabilities
85 ~~~~~~~~~~~~
86
87 Each remote helper is expected to support only a subset of commands.
88 The operations a helper supports are declared to Git in the response
89 to the `capabilities` command (see COMMANDS, below).
90
91 In the following, we list all defined capabilities and for
92 each we list which commands a helper with that capability
93 must provide.
94
95 Capabilities for Pushing
96 ^^^^^^^^^^^^^^^^^^^^^^^^
97 'connect'::
98 Can attempt to connect to 'git receive-pack' (for pushing),
99 'git upload-pack', etc for communication using
100 git's native packfile protocol. This
101 requires a bidirectional, full-duplex connection.
102 +
103 Supported commands: 'connect'.
104
105 'stateless-connect'::
106 Experimental; for internal use only.
107 Can attempt to connect to a remote server for communication
108 using git's wire-protocol version 2. See the documentation
109 for the stateless-connect command for more information.
110 +
111 Supported commands: 'stateless-connect'.
112
113 'push'::
114 Can discover remote refs and push local commits and the
115 history leading up to them to new or existing remote refs.
116 +
117 Supported commands: 'list for-push', 'push'.
118
119 'export'::
120 Can discover remote refs and push specified objects from a
121 fast-import stream to remote refs.
122 +
123 Supported commands: 'list for-push', 'export'.
124
125 If a helper advertises 'connect', Git will use it if possible and
126 fall back to another capability if the helper requests so when
127 connecting (see the 'connect' command under COMMANDS).
128 When choosing between 'push' and 'export', Git prefers 'push'.
129 Other frontends may have some other order of preference.
130
131 'no-private-update'::
132 When using the 'refspec' capability, git normally updates the
133 private ref on successful push. This update is disabled when
134 the remote-helper declares the capability 'no-private-update'.
135
136
137 Capabilities for Fetching
138 ^^^^^^^^^^^^^^^^^^^^^^^^^
139 'connect'::
140 Can try to connect to 'git upload-pack' (for fetching),
141 'git receive-pack', etc for communication using the
142 Git's native packfile protocol. This
143 requires a bidirectional, full-duplex connection.
144 +
145 Supported commands: 'connect'.
146
147 'stateless-connect'::
148 Experimental; for internal use only.
149 Can attempt to connect to a remote server for communication
150 using git's wire-protocol version 2. See the documentation
151 for the stateless-connect command for more information.
152 +
153 Supported commands: 'stateless-connect'.
154
155 'fetch'::
156 Can discover remote refs and transfer objects reachable from
157 them to the local object store.
158 +
159 Supported commands: 'list', 'fetch'.
160
161 'import'::
162 Can discover remote refs and output objects reachable from
163 them as a stream in fast-import format.
164 +
165 Supported commands: 'list', 'import'.
166
167 'check-connectivity'::
168 Can guarantee that when a clone is requested, the received
169 pack is self contained and is connected.
170
171 If a helper advertises 'connect', Git will use it if possible and
172 fall back to another capability if the helper requests so when
173 connecting (see the 'connect' command under COMMANDS).
174 When choosing between 'fetch' and 'import', Git prefers 'fetch'.
175 Other frontends may have some other order of preference.
176
177 Miscellaneous capabilities
178 ^^^^^^^^^^^^^^^^^^^^^^^^^^
179
180 'option'::
181 For specifying settings like `verbosity` (how much output to
182 write to stderr) and `depth` (how much history is wanted in the
183 case of a shallow clone) that affect how other commands are
184 carried out.
185
186 'refspec' <refspec>::
187 For remote helpers that implement 'import' or 'export', this capability
188 allows the refs to be constrained to a private namespace, instead of
189 writing to refs/heads or refs/remotes directly.
190 It is recommended that all importers providing the 'import'
191 capability use this. It's mandatory for 'export'.
192 +
193 A helper advertising the capability
194 `refspec refs/heads/*:refs/svn/origin/branches/*`
195 is saying that, when it is asked to `import refs/heads/topic`, the
196 stream it outputs will update the `refs/svn/origin/branches/topic`
197 ref.
198 +
199 This capability can be advertised multiple times. The first
200 applicable refspec takes precedence. The left-hand of refspecs
201 advertised with this capability must cover all refs reported by
202 the list command. If no 'refspec' capability is advertised,
203 there is an implied `refspec *:*`.
204 +
205 When writing remote-helpers for decentralized version control
206 systems, it is advised to keep a local copy of the repository to
207 interact with, and to let the private namespace refs point to this
208 local repository, while the refs/remotes namespace is used to track
209 the remote repository.
210
211 'bidi-import'::
212 This modifies the 'import' capability.
213 The fast-import commands 'cat-blob' and 'ls' can be used by remote-helpers
214 to retrieve information about blobs and trees that already exist in
215 fast-import's memory. This requires a channel from fast-import to the
216 remote-helper.
217 If it is advertised in addition to "import", Git establishes a pipe from
218 fast-import to the remote-helper's stdin.
219 It follows that Git and fast-import are both connected to the
220 remote-helper's stdin. Because Git can send multiple commands to
221 the remote-helper it is required that helpers that use 'bidi-import'
222 buffer all 'import' commands of a batch before sending data to fast-import.
223 This is to prevent mixing commands and fast-import responses on the
224 helper's stdin.
225
226 'export-marks' <file>::
227 This modifies the 'export' capability, instructing Git to dump the
228 internal marks table to <file> when complete. For details,
229 read up on `--export-marks=<file>` in linkgit:git-fast-export[1].
230
231 'import-marks' <file>::
232 This modifies the 'export' capability, instructing Git to load the
233 marks specified in <file> before processing any input. For details,
234 read up on `--import-marks=<file>` in linkgit:git-fast-export[1].
235
236 'signed-tags'::
237 This modifies the 'export' capability, instructing Git to pass
238 `--signed-tags=verbatim` to linkgit:git-fast-export[1]. In the
239 absence of this capability, Git will use `--signed-tags=warn-strip`.
240
241
242
243 COMMANDS
244 --------
245
246 Commands are given by the caller on the helper's standard input, one per line.
247
248 'capabilities'::
249 Lists the capabilities of the helper, one per line, ending
250 with a blank line. Each capability may be preceded with '*',
251 which marks them mandatory for Git versions using the remote
252 helper to understand. Any unknown mandatory capability is a
253 fatal error.
254 +
255 Support for this command is mandatory.
256
257 'list'::
258 Lists the refs, one per line, in the format "<value> <name>
259 [<attr> ...]". The value may be a hex sha1 hash, "@<dest>" for
260 a symref, or "?" to indicate that the helper could not get the
261 value of the ref. A space-separated list of attributes follows
262 the name; unrecognized attributes are ignored. The list ends
263 with a blank line.
264 +
265 See REF LIST ATTRIBUTES for a list of currently defined attributes.
266 +
267 Supported if the helper has the "fetch" or "import" capability.
268
269 'list for-push'::
270 Similar to 'list', except that it is used if and only if
271 the caller wants to the resulting ref list to prepare
272 push commands.
273 A helper supporting both push and fetch can use this
274 to distinguish for which operation the output of 'list'
275 is going to be used, possibly reducing the amount
276 of work that needs to be performed.
277 +
278 Supported if the helper has the "push" or "export" capability.
279
280 'option' <name> <value>::
281 Sets the transport helper option <name> to <value>. Outputs a
282 single line containing one of 'ok' (option successfully set),
283 'unsupported' (option not recognized) or 'error <msg>'
284 (option <name> is supported but <value> is not valid
285 for it). Options should be set before other commands,
286 and may influence the behavior of those commands.
287 +
288 See OPTIONS for a list of currently defined options.
289 +
290 Supported if the helper has the "option" capability.
291
292 'fetch' <sha1> <name>::
293 Fetches the given object, writing the necessary objects
294 to the database. Fetch commands are sent in a batch, one
295 per line, terminated with a blank line.
296 Outputs a single blank line when all fetch commands in the
297 same batch are complete. Only objects which were reported
298 in the output of 'list' with a sha1 may be fetched this way.
299 +
300 Optionally may output a 'lock <file>' line indicating a file under
301 GIT_DIR/objects/pack which is keeping a pack until refs can be
302 suitably updated.
303 +
304 If option 'check-connectivity' is requested, the helper must output
305 'connectivity-ok' if the clone is self-contained and connected.
306 +
307 Supported if the helper has the "fetch" capability.
308
309 'push' +<src>:<dst>::
310 Pushes the given local <src> commit or branch to the
311 remote branch described by <dst>. A batch sequence of
312 one or more 'push' commands is terminated with a blank line
313 (if there is only one reference to push, a single 'push' command
314 is followed by a blank line). For example, the following would
315 be two batches of 'push', the first asking the remote-helper
316 to push the local ref 'master' to the remote ref 'master' and
317 the local `HEAD` to the remote 'branch', and the second
318 asking to push ref 'foo' to ref 'bar' (forced update requested
319 by the '+').
320 +
321 ------------
322 push refs/heads/master:refs/heads/master
323 push HEAD:refs/heads/branch
324 \n
325 push +refs/heads/foo:refs/heads/bar
326 \n
327 ------------
328 +
329 Zero or more protocol options may be entered after the last 'push'
330 command, before the batch's terminating blank line.
331 +
332 When the push is complete, outputs one or more 'ok <dst>' or
333 'error <dst> <why>?' lines to indicate success or failure of
334 each pushed ref. The status report output is terminated by
335 a blank line. The option field <why> may be quoted in a C
336 style string if it contains an LF.
337 +
338 Supported if the helper has the "push" capability.
339
340 'import' <name>::
341 Produces a fast-import stream which imports the current value
342 of the named ref. It may additionally import other refs as
343 needed to construct the history efficiently. The script writes
344 to a helper-specific private namespace. The value of the named
345 ref should be written to a location in this namespace derived
346 by applying the refspecs from the "refspec" capability to the
347 name of the ref.
348 +
349 Especially useful for interoperability with a foreign versioning
350 system.
351 +
352 Just like 'push', a batch sequence of one or more 'import' is
353 terminated with a blank line. For each batch of 'import', the remote
354 helper should produce a fast-import stream terminated by a 'done'
355 command.
356 +
357 Note that if the 'bidi-import' capability is used the complete batch
358 sequence has to be buffered before starting to send data to fast-import
359 to prevent mixing of commands and fast-import responses on the helper's
360 stdin.
361 +
362 Supported if the helper has the "import" capability.
363
364 'export'::
365 Instructs the remote helper that any subsequent input is
366 part of a fast-import stream (generated by 'git fast-export')
367 containing objects which should be pushed to the remote.
368 +
369 Especially useful for interoperability with a foreign versioning
370 system.
371 +
372 The 'export-marks' and 'import-marks' capabilities, if specified,
373 affect this command in so far as they are passed on to 'git
374 fast-export', which then will load/store a table of marks for
375 local objects. This can be used to implement for incremental
376 operations.
377 +
378 Supported if the helper has the "export" capability.
379
380 'connect' <service>::
381 Connects to given service. Standard input and standard output
382 of helper are connected to specified service (git prefix is
383 included in service name so e.g. fetching uses 'git-upload-pack'
384 as service) on remote side. Valid replies to this command are
385 empty line (connection established), 'fallback' (no smart
386 transport support, fall back to dumb transports) and just
387 exiting with error message printed (can't connect, don't
388 bother trying to fall back). After line feed terminating the
389 positive (empty) response, the output of service starts. After
390 the connection ends, the remote helper exits.
391 +
392 Supported if the helper has the "connect" capability.
393
394 'stateless-connect' <service>::
395 Experimental; for internal use only.
396 Connects to the given remote service for communication using
397 git's wire-protocol version 2. Valid replies to this command
398 are empty line (connection established), 'fallback' (no smart
399 transport support, fall back to dumb transports) and just
400 exiting with error message printed (can't connect, don't bother
401 trying to fall back). After line feed terminating the positive
402 (empty) response, the output of the service starts. Messages
403 (both request and response) must consist of zero or more
404 PKT-LINEs, terminating in a flush packet. The client must not
405 expect the server to store any state in between request-response
406 pairs. After the connection ends, the remote helper exits.
407 +
408 Supported if the helper has the "stateless-connect" capability.
409
410 If a fatal error occurs, the program writes the error message to
411 stderr and exits. The caller should expect that a suitable error
412 message has been printed if the child closes the connection without
413 completing a valid response for the current command.
414
415 Additional commands may be supported, as may be determined from
416 capabilities reported by the helper.
417
418 REF LIST ATTRIBUTES
419 -------------------
420
421 The 'list' command produces a list of refs in which each ref
422 may be followed by a list of attributes. The following ref list
423 attributes are defined.
424
425 'unchanged'::
426 This ref is unchanged since the last import or fetch, although
427 the helper cannot necessarily determine what value that produced.
428
429 OPTIONS
430 -------
431
432 The following options are defined and (under suitable circumstances)
433 set by Git if the remote helper has the 'option' capability.
434
435 'option verbosity' <n>::
436 Changes the verbosity of messages displayed by the helper.
437 A value of 0 for <n> means that processes operate
438 quietly, and the helper produces only error output.
439 1 is the default level of verbosity, and higher values
440 of <n> correspond to the number of -v flags passed on the
441 command line.
442
443 'option progress' {'true'|'false'}::
444 Enables (or disables) progress messages displayed by the
445 transport helper during a command.
446
447 'option depth' <depth>::
448 Deepens the history of a shallow repository.
449
450 'option deepen-since <timestamp>::
451 Deepens the history of a shallow repository based on time.
452
453 'option deepen-not <ref>::
454 Deepens the history of a shallow repository excluding ref.
455 Multiple options add up.
456
457 'option deepen-relative {'true'|'false'}::
458 Deepens the history of a shallow repository relative to
459 current boundary. Only valid when used with "option depth".
460
461 'option followtags' {'true'|'false'}::
462 If enabled the helper should automatically fetch annotated
463 tag objects if the object the tag points at was transferred
464 during the fetch command. If the tag is not fetched by
465 the helper a second fetch command will usually be sent to
466 ask for the tag specifically. Some helpers may be able to
467 use this option to avoid a second network connection.
468
469 'option dry-run' {'true'|'false'}:
470 If true, pretend the operation completed successfully,
471 but don't actually change any repository data. For most
472 helpers this only applies to the 'push', if supported.
473
474 'option servpath <c-style-quoted-path>'::
475 Sets service path (--upload-pack, --receive-pack etc.) for
476 next connect. Remote helper may support this option, but
477 must not rely on this option being set before
478 connect request occurs.
479
480 'option check-connectivity' {'true'|'false'}::
481 Request the helper to check connectivity of a clone.
482
483 'option force' {'true'|'false'}::
484 Request the helper to perform a force update. Defaults to
485 'false'.
486
487 'option cloning' {'true'|'false'}::
488 Notify the helper this is a clone request (i.e. the current
489 repository is guaranteed empty).
490
491 'option update-shallow' {'true'|'false'}::
492 Allow to extend .git/shallow if the new refs require it.
493
494 'option pushcert' {'true'|'false'}::
495 GPG sign pushes.
496
497 'option push-option <string>::
498 Transmit <string> as a push option. As the push option
499 must not contain LF or NUL characters, the string is not encoded.
500
501 'option from-promisor' {'true'|'false'}::
502 Indicate that these objects are being fetched from a promisor.
503
504 'option no-dependents' {'true'|'false'}::
505 Indicate that only the objects wanted need to be fetched, not
506 their dependents.
507
508 SEE ALSO
509 --------
510 linkgit:git-remote[1]
511
512 linkgit:git-remote-ext[1]
513
514 linkgit:git-remote-fd[1]
515
516 linkgit:git-remote-testgit[1]
517
518 linkgit:git-fast-import[1]
519
520 GIT
521 ---
522 Part of the linkgit:git[1] suite