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