Merge branch 'jc/mkstemp-more-careful-error-reporting'
[git/git.git] / Documentation / git-remote-helpers.txt
1 git-remote-helpers(1)
2 =====================
5 ----
6 git-remote-helpers - Helper programs to interact with remote repositories
9 --------
10 [verse]
11 'git remote-<transport>' <repository> [<URL>]
14 -----------
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.
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.
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'.
39 ----------
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.
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.
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.
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.
70 ------------
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.
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.
84 Capabilities
85 ~~~~~~~~~~~~
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).
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.
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'.
105 'push'::
106 Can discover remote refs and push local commits and the
107 history leading up to them to new or existing remote refs.
108 +
109 Supported commands: 'list for-push', 'push'.
111 'export'::
112 Can discover remote refs and push specified objects from a
113 fast-import stream to remote refs.
114 +
115 Supported commands: 'list for-push', 'export'.
117 If a helper advertises 'connect', git will use it if possible and
118 fall back to another capability if the helper requests so when
119 connecting (see the 'connect' command under COMMANDS).
120 When choosing between 'push' and 'export', git prefers 'push'.
121 Other frontends may have some other order of preference.
124 Capabilities for Fetching
125 ^^^^^^^^^^^^^^^^^^^^^^^^^
126 'connect'::
127 Can try to connect to 'git upload-pack' (for fetching),
128 'git receive-pack', etc for communication using the
129 git's native packfile protocol. This
130 requires a bidirectional, full-duplex connection.
131 +
132 Supported commands: 'connect'.
134 'fetch'::
135 Can discover remote refs and transfer objects reachable from
136 them to the local object store.
137 +
138 Supported commands: 'list', 'fetch'.
140 'import'::
141 Can discover remote refs and output objects reachable from
142 them as a stream in fast-import format.
143 +
144 Supported commands: 'list', 'import'.
146 If a helper advertises 'connect', git will use it if possible and
147 fall back to another capability if the helper requests so when
148 connecting (see the 'connect' command under COMMANDS).
149 When choosing between 'fetch' and 'import', git prefers 'fetch'.
150 Other frontends may have some other order of preference.
152 Miscellaneous capabilities
153 ^^^^^^^^^^^^^^^^^^^^^^^^^^
155 'option'::
156 For specifying settings like `verbosity` (how much output to
157 write to stderr) and `depth` (how much history is wanted in the
158 case of a shallow clone) that affect how other commands are
159 carried out.
161 'refspec' <refspec>::
162 This modifies the 'import' capability, allowing the produced
163 fast-import stream to modify refs in a private namespace
164 instead of writing to refs/heads or refs/remotes directly.
165 It is recommended that all importers providing the 'import'
166 capability use this.
167 +
168 A helper advertising the capability
169 `refspec refs/heads/*:refs/svn/origin/branches/*`
170 is saying that, when it is asked to `import refs/heads/topic`, the
171 stream it outputs will update the `refs/svn/origin/branches/topic`
172 ref.
173 +
174 This capability can be advertised multiple times. The first
175 applicable refspec takes precedence. The left-hand of refspecs
176 advertised with this capability must cover all refs reported by
177 the list command. If no 'refspec' capability is advertised,
178 there is an implied `refspec *:*`.
180 'bidi-import'::
181 This modifies the 'import' capability.
182 The fast-import commands 'cat-blob' and 'ls' can be used by remote-helpers
183 to retrieve information about blobs and trees that already exist in
184 fast-import's memory. This requires a channel from fast-import to the
185 remote-helper.
186 If it is advertised in addition to "import", git establishes a pipe from
187 fast-import to the remote-helper's stdin.
188 It follows that git and fast-import are both connected to the
189 remote-helper's stdin. Because git can send multiple commands to
190 the remote-helper it is required that helpers that use 'bidi-import'
191 buffer all 'import' commands of a batch before sending data to fast-import.
192 This is to prevent mixing commands and fast-import responses on the
193 helper's stdin.
195 'export-marks' <file>::
196 This modifies the 'export' capability, instructing git to dump the
197 internal marks table to <file> when complete. For details,
198 read up on '--export-marks=<file>' in linkgit:git-fast-export[1].
200 'import-marks' <file>::
201 This modifies the 'export' capability, instructing git to load the
202 marks specified in <file> before processing any input. For details,
203 read up on '--import-marks=<file>' in linkgit:git-fast-export[1].
209 --------
211 Commands are given by the caller on the helper's standard input, one per line.
213 'capabilities'::
214 Lists the capabilities of the helper, one per line, ending
215 with a blank line. Each capability may be preceded with '*',
216 which marks them mandatory for git versions using the remote
217 helper to understand. Any unknown mandatory capability is a
218 fatal error.
219 +
220 Support for this command is mandatory.
222 'list'::
223 Lists the refs, one per line, in the format "<value> <name>
224 [<attr> ...]". The value may be a hex sha1 hash, "@<dest>" for
225 a symref, or "?" to indicate that the helper could not get the
226 value of the ref. A space-separated list of attributes follows
227 the name; unrecognized attributes are ignored. The list ends
228 with a blank line.
229 +
230 See REF LIST ATTRIBUTES for a list of currently defined attributes.
231 +
232 Supported if the helper has the "fetch" or "import" capability.
234 'list for-push'::
235 Similar to 'list', except that it is used if and only if
236 the caller wants to the resulting ref list to prepare
237 push commands.
238 A helper supporting both push and fetch can use this
239 to distinguish for which operation the output of 'list'
240 is going to be used, possibly reducing the amount
241 of work that needs to be performed.
242 +
243 Supported if the helper has the "push" or "export" capability.
245 'option' <name> <value>::
246 Sets the transport helper option <name> to <value>. Outputs a
247 single line containing one of 'ok' (option successfully set),
248 'unsupported' (option not recognized) or 'error <msg>'
249 (option <name> is supported but <value> is not valid
250 for it). Options should be set before other commands,
251 and may influence the behavior of those commands.
252 +
253 See OPTIONS for a list of currently defined options.
254 +
255 Supported if the helper has the "option" capability.
257 'fetch' <sha1> <name>::
258 Fetches the given object, writing the necessary objects
259 to the database. Fetch commands are sent in a batch, one
260 per line, terminated with a blank line.
261 Outputs a single blank line when all fetch commands in the
262 same batch are complete. Only objects which were reported
263 in the output of 'list' with a sha1 may be fetched this way.
264 +
265 Optionally may output a 'lock <file>' line indicating a file under
266 GIT_DIR/objects/pack which is keeping a pack until refs can be
267 suitably updated.
268 +
269 Supported if the helper has the "fetch" capability.
271 'push' +<src>:<dst>::
272 Pushes the given local <src> commit or branch to the
273 remote branch described by <dst>. A batch sequence of
274 one or more 'push' commands is terminated with a blank line
275 (if there is only one reference to push, a single 'push' command
276 is followed by a blank line). For example, the following would
277 be two batches of 'push', the first asking the remote-helper
278 to push the local ref 'master' to the remote ref 'master' and
279 the local 'HEAD' to the remote 'branch', and the second
280 asking to push ref 'foo' to ref 'bar' (forced update requested
281 by the '+').
282 +
283 ------------
284 push refs/heads/master:refs/heads/master
285 push HEAD:refs/heads/branch
286 \n
287 push +refs/heads/foo:refs/heads/bar
288 \n
289 ------------
290 +
291 Zero or more protocol options may be entered after the last 'push'
292 command, before the batch's terminating blank line.
293 +
294 When the push is complete, outputs one or more 'ok <dst>' or
295 'error <dst> <why>?' lines to indicate success or failure of
296 each pushed ref. The status report output is terminated by
297 a blank line. The option field <why> may be quoted in a C
298 style string if it contains an LF.
299 +
300 Supported if the helper has the "push" capability.
302 'import' <name>::
303 Produces a fast-import stream which imports the current value
304 of the named ref. It may additionally import other refs as
305 needed to construct the history efficiently. The script writes
306 to a helper-specific private namespace. The value of the named
307 ref should be written to a location in this namespace derived
308 by applying the refspecs from the "refspec" capability to the
309 name of the ref.
310 +
311 Especially useful for interoperability with a foreign versioning
312 system.
313 +
314 Just like 'push', a batch sequence of one or more 'import' is
315 terminated with a blank line. For each batch of 'import', the remote
316 helper should produce a fast-import stream terminated by a 'done'
317 command.
318 +
319 Note that if the 'bidi-import' capability is used the complete batch
320 sequence has to be buffered before starting to send data to fast-import
321 to prevent mixing of commands and fast-import responses on the helper's
322 stdin.
323 +
324 Supported if the helper has the "import" capability.
326 'export'::
327 Instructs the remote helper that any subsequent input is
328 part of a fast-import stream (generated by 'git fast-export')
329 containing objects which should be pushed to the remote.
330 +
331 Especially useful for interoperability with a foreign versioning
332 system.
333 +
334 The 'export-marks' and 'import-marks' capabilities, if specified,
335 affect this command in so far as they are passed on to 'git
336 fast-export', which then will load/store a table of marks for
337 local objects. This can be used to implement for incremental
338 operations.
339 +
340 Supported if the helper has the "export" capability.
342 'connect' <service>::
343 Connects to given service. Standard input and standard output
344 of helper are connected to specified service (git prefix is
345 included in service name so e.g. fetching uses 'git-upload-pack'
346 as service) on remote side. Valid replies to this command are
347 empty line (connection established), 'fallback' (no smart
348 transport support, fall back to dumb transports) and just
349 exiting with error message printed (can't connect, don't
350 bother trying to fall back). After line feed terminating the
351 positive (empty) response, the output of service starts. After
352 the connection ends, the remote helper exits.
353 +
354 Supported if the helper has the "connect" capability.
356 If a fatal error occurs, the program writes the error message to
357 stderr and exits. The caller should expect that a suitable error
358 message has been printed if the child closes the connection without
359 completing a valid response for the current command.
361 Additional commands may be supported, as may be determined from
362 capabilities reported by the helper.
365 -------------------
367 The 'list' command produces a list of refs in which each ref
368 may be followed by a list of attributes. The following ref list
369 attributes are defined.
371 'unchanged'::
372 This ref is unchanged since the last import or fetch, although
373 the helper cannot necessarily determine what value that produced.
376 -------
378 The following options are defined and (under suitable circumstances)
379 set by git if the remote helper has the 'option' capability.
381 'option verbosity' <n>::
382 Changes the verbosity of messages displayed by the helper.
383 A value of 0 for <n> means that processes operate
384 quietly, and the helper produces only error output.
385 1 is the default level of verbosity, and higher values
386 of <n> correspond to the number of -v flags passed on the
387 command line.
389 'option progress' \{'true'|'false'\}::
390 Enables (or disables) progress messages displayed by the
391 transport helper during a command.
393 'option depth' <depth>::
394 Deepens the history of a shallow repository.
396 'option followtags' \{'true'|'false'\}::
397 If enabled the helper should automatically fetch annotated
398 tag objects if the object the tag points at was transferred
399 during the fetch command. If the tag is not fetched by
400 the helper a second fetch command will usually be sent to
401 ask for the tag specifically. Some helpers may be able to
402 use this option to avoid a second network connection.
404 'option dry-run' \{'true'|'false'\}:
405 If true, pretend the operation completed successfully,
406 but don't actually change any repository data. For most
407 helpers this only applies to the 'push', if supported.
409 'option servpath <c-style-quoted-path>'::
410 Sets service path (--upload-pack, --receive-pack etc.) for
411 next connect. Remote helper may support this option, but
412 must not rely on this option being set before
413 connect request occurs.
416 --------
417 linkgit:git-remote[1]
419 linkgit:git-remote-testgit[1]
421 GIT
422 ---
423 Part of the linkgit:git[1] suite