remote-bzr: detect local repositories
[git/git.git] / Documentation / git-remote-helpers.txt
1 git-remote-helpers(1)
2 =====================
3
4 NAME
5 ----
6 git-remote-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 INPUT FORMAT
39 ------------
40
41 Git sends the remote helper a list of commands on standard input, one
42 per line. The first command is always the 'capabilities' command, in
43 response to which the remote helper must print a list of the
44 capabilities it supports (see below) followed by a blank line. The
45 response to the capabilities command determines what commands Git uses
46 in the remainder of the command stream.
47
48 The command stream is terminated by a blank line. In some cases
49 (indicated in the documentation of the relevant commands), this blank
50 line is followed by a payload in some other protocol (e.g., the pack
51 protocol), while in others it indicates the end of input.
52
53 Capabilities
54 ~~~~~~~~~~~~
55
56 Each remote helper is expected to support only a subset of commands.
57 The operations a helper supports are declared to git in the response
58 to the `capabilities` command (see COMMANDS, below).
59
60 'option'::
61 For specifying settings like `verbosity` (how much output to
62 write to stderr) and `depth` (how much history is wanted in the
63 case of a shallow clone) that affect how other commands are
64 carried out.
65
66 'connect'::
67 For fetching and pushing using git's native packfile protocol
68 that requires a bidirectional, full-duplex connection.
69
70 'push'::
71 For listing remote refs and pushing specified objects from the
72 local object store to remote refs.
73
74 'fetch'::
75 For listing remote refs and fetching the associated history to
76 the local object store.
77
78 'import'::
79 For listing remote refs and fetching the associated history as
80 a fast-import stream.
81
82 'refspec' <refspec>::
83 This modifies the 'import' capability, allowing the produced
84 fast-import stream to modify refs in a private namespace
85 instead of writing to refs/heads or refs/remotes directly.
86 It is recommended that all importers providing the 'import'
87 capability use this.
88 +
89 A helper advertising the capability
90 `refspec refs/heads/*:refs/svn/origin/branches/*`
91 is saying that, when it is asked to `import refs/heads/topic`, the
92 stream it outputs will update the `refs/svn/origin/branches/topic`
93 ref.
94 +
95 This capability can be advertised multiple times. The first
96 applicable refspec takes precedence. The left-hand of refspecs
97 advertised with this capability must cover all refs reported by
98 the list command. If no 'refspec' capability is advertised,
99 there is an implied `refspec *:*`.
100
101 'bidi-import'::
102 The fast-import commands 'cat-blob' and 'ls' can be used by remote-helpers
103 to retrieve information about blobs and trees that already exist in
104 fast-import's memory. This requires a channel from fast-import to the
105 remote-helper.
106 If it is advertised in addition to "import", git establishes a pipe from
107 fast-import to the remote-helper's stdin.
108 It follows that git and fast-import are both connected to the
109 remote-helper's stdin. Because git can send multiple commands to
110 the remote-helper it is required that helpers that use 'bidi-import'
111 buffer all 'import' commands of a batch before sending data to fast-import.
112 This is to prevent mixing commands and fast-import responses on the
113 helper's stdin.
114
115 Capabilities for Pushing
116 ~~~~~~~~~~~~~~~~~~~~~~~~
117 'connect'::
118 Can attempt to connect to 'git receive-pack' (for pushing),
119 'git upload-pack', etc for communication using the
120 packfile protocol.
121 +
122 Supported commands: 'connect'.
123
124 'push'::
125 Can discover remote refs and push local commits and the
126 history leading up to them to new or existing remote refs.
127 +
128 Supported commands: 'list for-push', 'push'.
129
130 If a helper advertises both 'connect' and 'push', git will use
131 'connect' if possible and fall back to 'push' if the helper requests
132 so when connecting (see the 'connect' command under COMMANDS).
133
134 Capabilities for Fetching
135 ~~~~~~~~~~~~~~~~~~~~~~~~~
136 'connect'::
137 Can try to connect to 'git upload-pack' (for fetching),
138 'git receive-pack', etc for communication using the
139 packfile protocol.
140 +
141 Supported commands: 'connect'.
142
143 'fetch'::
144 Can discover remote refs and transfer objects reachable from
145 them to the local object store.
146 +
147 Supported commands: 'list', 'fetch'.
148
149 'import'::
150 Can discover remote refs and output objects reachable from
151 them as a stream in fast-import format.
152 +
153 Supported commands: 'list', 'import'.
154
155 If a helper advertises 'connect', git will use it if possible and
156 fall back to another capability if the helper requests so when
157 connecting (see the 'connect' command under COMMANDS).
158 When choosing between 'fetch' and 'import', git prefers 'fetch'.
159 Other frontends may have some other order of preference.
160
161 'refspec' <refspec>::
162 This modifies the 'import' capability.
163 +
164 A helper advertising
165 `refspec refs/heads/*:refs/svn/origin/branches/*`
166 in its capabilities is saying that, when it handles
167 `import refs/heads/topic`, the stream it outputs will update the
168 `refs/svn/origin/branches/topic` ref.
169 +
170 This capability can be advertised multiple times. The first
171 applicable refspec takes precedence. The left-hand of refspecs
172 advertised with this capability must cover all refs reported by
173 the list command. If no 'refspec' capability is advertised,
174 there is an implied `refspec *:*`.
175
176 INVOCATION
177 ----------
178
179 Remote helper programs are invoked with one or (optionally) two
180 arguments. The first argument specifies a remote repository as in git;
181 it is either the name of a configured remote or a URL. The second
182 argument specifies a URL; it is usually of the form
183 '<transport>://<address>', but any arbitrary string is possible.
184 The 'GIT_DIR' environment variable is set up for the remote helper
185 and can be used to determine where to store additional data or from
186 which directory to invoke auxiliary git commands.
187
188 When git encounters a URL of the form '<transport>://<address>', where
189 '<transport>' is a protocol that it cannot handle natively, it
190 automatically invokes 'git remote-<transport>' with the full URL as
191 the second argument. If such a URL is encountered directly on the
192 command line, the first argument is the same as the second, and if it
193 is encountered in a configured remote, the first argument is the name
194 of that remote.
195
196 A URL of the form '<transport>::<address>' explicitly instructs git to
197 invoke 'git remote-<transport>' with '<address>' as the second
198 argument. If such a URL is encountered directly on the command line,
199 the first argument is '<address>', and if it is encountered in a
200 configured remote, the first argument is the name of that remote.
201
202 Additionally, when a configured remote has 'remote.<name>.vcs' set to
203 '<transport>', git explicitly invokes 'git remote-<transport>' with
204 '<name>' as the first argument. If set, the second argument is
205 'remote.<name>.url'; otherwise, the second argument is omitted.
206
207 COMMANDS
208 --------
209
210 Commands are given by the caller on the helper's standard input, one per line.
211
212 'capabilities'::
213 Lists the capabilities of the helper, one per line, ending
214 with a blank line. Each capability may be preceded with '*',
215 which marks them mandatory for git version using the remote
216 helper to understand (unknown mandatory capability is fatal
217 error).
218
219 'list'::
220 Lists the refs, one per line, in the format "<value> <name>
221 [<attr> ...]". The value may be a hex sha1 hash, "@<dest>" for
222 a symref, or "?" to indicate that the helper could not get the
223 value of the ref. A space-separated list of attributes follows
224 the name; unrecognized attributes are ignored. The list ends
225 with a blank line.
226 +
227 If 'push' is supported this may be called as 'list for-push'
228 to obtain the current refs prior to sending one or more 'push'
229 commands to the helper.
230
231 'option' <name> <value>::
232 Sets the transport helper option <name> to <value>. Outputs a
233 single line containing one of 'ok' (option successfully set),
234 'unsupported' (option not recognized) or 'error <msg>'
235 (option <name> is supported but <value> is not valid
236 for it). Options should be set before other commands,
237 and may influence the behavior of those commands.
238 +
239 Supported if the helper has the "option" capability.
240
241 'fetch' <sha1> <name>::
242 Fetches the given object, writing the necessary objects
243 to the database. Fetch commands are sent in a batch, one
244 per line, terminated with a blank line.
245 Outputs a single blank line when all fetch commands in the
246 same batch are complete. Only objects which were reported
247 in the ref list with a sha1 may be fetched this way.
248 +
249 Optionally may output a 'lock <file>' line indicating a file under
250 GIT_DIR/objects/pack which is keeping a pack until refs can be
251 suitably updated.
252 +
253 Supported if the helper has the "fetch" capability.
254
255 'push' +<src>:<dst>::
256 Pushes the given local <src> commit or branch to the
257 remote branch described by <dst>. A batch sequence of
258 one or more 'push' commands is terminated with a blank line
259 (if there is only one reference to push, a single 'push' command
260 is followed by a blank line). For example, the following would
261 be two batches of 'push', the first asking the remote-helper
262 to push the local ref 'master' to the remote ref 'master' and
263 the local 'HEAD' to the remote 'branch', and the second
264 asking to push ref 'foo' to ref 'bar' (forced update requested
265 by the '+').
266 +
267 ------------
268 push refs/heads/master:refs/heads/master
269 push HEAD:refs/heads/branch
270 \n
271 push +refs/heads/foo:refs/heads/bar
272 \n
273 ------------
274 +
275 Zero or more protocol options may be entered after the last 'push'
276 command, before the batch's terminating blank line.
277 +
278 When the push is complete, outputs one or more 'ok <dst>' or
279 'error <dst> <why>?' lines to indicate success or failure of
280 each pushed ref. The status report output is terminated by
281 a blank line. The option field <why> may be quoted in a C
282 style string if it contains an LF.
283 +
284 Supported if the helper has the "push" capability.
285
286 'import' <name>::
287 Produces a fast-import stream which imports the current value
288 of the named ref. It may additionally import other refs as
289 needed to construct the history efficiently. The script writes
290 to a helper-specific private namespace. The value of the named
291 ref should be written to a location in this namespace derived
292 by applying the refspecs from the "refspec" capability to the
293 name of the ref.
294 +
295 Especially useful for interoperability with a foreign versioning
296 system.
297 +
298 Just like 'push', a batch sequence of one or more 'import' is
299 terminated with a blank line. For each batch of 'import', the remote
300 helper should produce a fast-import stream terminated by a 'done'
301 command.
302 +
303 Note that if the 'bidi-import' capability is used the complete batch
304 sequence has to be buffered before starting to send data to fast-import
305 to prevent mixing of commands and fast-import responses on the helper's
306 stdin.
307 +
308 Supported if the helper has the 'import' capability.
309
310 'connect' <service>::
311 Connects to given service. Standard input and standard output
312 of helper are connected to specified service (git prefix is
313 included in service name so e.g. fetching uses 'git-upload-pack'
314 as service) on remote side. Valid replies to this command are
315 empty line (connection established), 'fallback' (no smart
316 transport support, fall back to dumb transports) and just
317 exiting with error message printed (can't connect, don't
318 bother trying to fall back). After line feed terminating the
319 positive (empty) response, the output of service starts. After
320 the connection ends, the remote helper exits.
321 +
322 Supported if the helper has the "connect" capability.
323
324 If a fatal error occurs, the program writes the error message to
325 stderr and exits. The caller should expect that a suitable error
326 message has been printed if the child closes the connection without
327 completing a valid response for the current command.
328
329 Additional commands may be supported, as may be determined from
330 capabilities reported by the helper.
331
332 REF LIST ATTRIBUTES
333 -------------------
334
335 'for-push'::
336 The caller wants to use the ref list to prepare push
337 commands. A helper might chose to acquire the ref list by
338 opening a different type of connection to the destination.
339
340 'unchanged'::
341 This ref is unchanged since the last import or fetch, although
342 the helper cannot necessarily determine what value that produced.
343
344 OPTIONS
345 -------
346 'option verbosity' <n>::
347 Changes the verbosity of messages displayed by the helper.
348 A value of 0 for <n> means that processes operate
349 quietly, and the helper produces only error output.
350 1 is the default level of verbosity, and higher values
351 of <n> correspond to the number of -v flags passed on the
352 command line.
353
354 'option progress' \{'true'|'false'\}::
355 Enables (or disables) progress messages displayed by the
356 transport helper during a command.
357
358 'option depth' <depth>::
359 Deepens the history of a shallow repository.
360
361 'option followtags' \{'true'|'false'\}::
362 If enabled the helper should automatically fetch annotated
363 tag objects if the object the tag points at was transferred
364 during the fetch command. If the tag is not fetched by
365 the helper a second fetch command will usually be sent to
366 ask for the tag specifically. Some helpers may be able to
367 use this option to avoid a second network connection.
368
369 'option dry-run' \{'true'|'false'\}:
370 If true, pretend the operation completed successfully,
371 but don't actually change any repository data. For most
372 helpers this only applies to the 'push', if supported.
373
374 'option servpath <c-style-quoted-path>'::
375 Sets service path (--upload-pack, --receive-pack etc.) for
376 next connect. Remote helper may support this option, but
377 must not rely on this option being set before
378 connect request occurs.
379
380 SEE ALSO
381 --------
382 linkgit:git-remote[1]
383
384 linkgit:git-remote-testgit[1]
385
386 GIT
387 ---
388 Part of the linkgit:git[1] suite