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1 | git-fast-import(1) |
2 | ================== | |
3 | ||
4 | NAME | |
5 | ---- | |
7a33631f | 6 | git-fast-import - Backend for fast Git data importers |
6e411d20 SP |
7 | |
8 | ||
9 | SYNOPSIS | |
10 | -------- | |
7791a1d9 | 11 | [verse] |
b1889c36 | 12 | frontend | 'git fast-import' [options] |
6e411d20 SP |
13 | |
14 | DESCRIPTION | |
15 | ----------- | |
16 | This program is usually not what the end user wants to run directly. | |
17 | Most end users want to use one of the existing frontend programs, | |
18 | which parses a specific type of foreign source and feeds the contents | |
0b444cdb | 19 | stored there to 'git fast-import'. |
6e411d20 | 20 | |
882227f1 | 21 | fast-import reads a mixed command/data stream from standard input and |
6e411d20 SP |
22 | writes one or more packfiles directly into the current repository. |
23 | When EOF is received on standard input, fast import writes out | |
24 | updated branch and tag refs, fully updating the current repository | |
25 | with the newly imported data. | |
26 | ||
882227f1 | 27 | The fast-import backend itself can import into an empty repository (one that |
0b444cdb | 28 | has already been initialized by 'git init') or incrementally |
6e411d20 SP |
29 | update an existing populated repository. Whether or not incremental |
30 | imports are supported from a particular foreign source depends on | |
31 | the frontend program in use. | |
32 | ||
33 | ||
34 | OPTIONS | |
35 | ------- | |
63e0c8b3 SP |
36 | --date-format=<fmt>:: |
37 | Specify the type of dates the frontend will supply to | |
882227f1 | 38 | fast-import within `author`, `committer` and `tagger` commands. |
63e0c8b3 SP |
39 | See ``Date Formats'' below for details about which formats |
40 | are supported, and their syntax. | |
41 | ||
7073e69e SP |
42 | --force:: |
43 | Force updating modified existing branches, even if doing | |
44 | so would cause commits to be lost (as the new commit does | |
45 | not contain the old commit). | |
46 | ||
6e411d20 | 47 | --max-pack-size=<n>:: |
4d0cc224 | 48 | Maximum size of each output packfile. |
89e0a3a1 | 49 | The default is unlimited. |
6e411d20 | 50 | |
5eef828b SP |
51 | --big-file-threshold=<n>:: |
52 | Maximum size of a blob that fast-import will attempt to | |
53 | create a delta for, expressed in bytes. The default is 512m | |
54 | (512 MiB). Some importers may wish to lower this on systems | |
55 | with constrained memory. | |
56 | ||
6e411d20 SP |
57 | --depth=<n>:: |
58 | Maximum delta depth, for blob and tree deltification. | |
59 | Default is 10. | |
60 | ||
61 | --active-branches=<n>:: | |
62 | Maximum number of branches to maintain active at once. | |
63 | See ``Memory Utilization'' below for details. Default is 5. | |
64 | ||
65 | --export-marks=<file>:: | |
66 | Dumps the internal marks table to <file> when complete. | |
67 | Marks are written one per line as `:markid SHA-1`. | |
68 | Frontends can use this file to validate imports after they | |
e8438420 SP |
69 | have been completed, or to save the marks table across |
70 | incremental runs. As <file> is only opened and truncated | |
71 | at checkpoint (or completion) the same path can also be | |
72 | safely given to \--import-marks. | |
73 | ||
74 | --import-marks=<file>:: | |
75 | Before processing any input, load the marks specified in | |
76 | <file>. The input file must exist, must be readable, and | |
77 | must use the same format as produced by \--export-marks. | |
78 | Multiple options may be supplied to import more than one | |
79 | set of marks. If a mark is defined to different values, | |
80 | the last file wins. | |
6e411d20 | 81 | |
dded4f12 RR |
82 | --import-marks-if-exists=<file>:: |
83 | Like --import-marks but instead of erroring out, silently | |
84 | skips the file if it does not exist. | |
85 | ||
bc3c79ae | 86 | --relative-marks:: |
9fee24ca | 87 | After specifying --relative-marks the paths specified |
bc3c79ae SR |
88 | with --import-marks= and --export-marks= are relative |
89 | to an internal directory in the current repository. | |
90 | In git-fast-import this means that the paths are relative | |
91 | to the .git/info/fast-import directory. However, other | |
92 | importers may use a different location. | |
93 | ||
94 | --no-relative-marks:: | |
95 | Negates a previous --relative-marks. Allows for combining | |
96 | relative and non-relative marks by interweaving | |
9fee24ca | 97 | --(no-)-relative-marks with the --(import|export)-marks= |
bc3c79ae SR |
98 | options. |
99 | ||
85c62395 DB |
100 | --cat-blob-fd=<fd>:: |
101 | Specify the file descriptor that will be written to | |
102 | when the `cat-blob` command is encountered in the stream. | |
103 | The default behaviour is to write to `stdout`. | |
104 | ||
bdf1c06d SP |
105 | --export-pack-edges=<file>:: |
106 | After creating a packfile, print a line of data to | |
107 | <file> listing the filename of the packfile and the last | |
108 | commit on each branch that was written to that packfile. | |
109 | This information may be useful after importing projects | |
110 | whose total object set exceeds the 4 GiB packfile limit, | |
111 | as these commits can be used as edge points during calls | |
0b444cdb | 112 | to 'git pack-objects'. |
bdf1c06d | 113 | |
c499d768 | 114 | --quiet:: |
882227f1 | 115 | Disable all non-fatal output, making fast-import silent when it |
7f9d77f2 | 116 | is successful. This option disables the output shown by |
c499d768 SP |
117 | \--stats. |
118 | ||
119 | --stats:: | |
882227f1 | 120 | Display some basic statistics about the objects fast-import has |
c499d768 | 121 | created, the packfiles they were stored into, and the |
882227f1 | 122 | memory used by fast-import during this run. Showing this output |
c499d768 SP |
123 | is currently the default, but can be disabled with \--quiet. |
124 | ||
125 | ||
6e411d20 SP |
126 | Performance |
127 | ----------- | |
882227f1 | 128 | The design of fast-import allows it to import large projects in a minimum |
6e411d20 | 129 | amount of memory usage and processing time. Assuming the frontend |
882227f1 | 130 | is able to keep up with fast-import and feed it a constant stream of data, |
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131 | import times for projects holding 10+ years of history and containing |
132 | 100,000+ individual commits are generally completed in just 1-2 | |
133 | hours on quite modest (~$2,000 USD) hardware. | |
134 | ||
135 | Most bottlenecks appear to be in foreign source data access (the | |
882227f1 | 136 | source just cannot extract revisions fast enough) or disk IO (fast-import |
6e411d20 SP |
137 | writes as fast as the disk will take the data). Imports will run |
138 | faster if the source data is stored on a different drive than the | |
139 | destination Git repository (due to less IO contention). | |
140 | ||
141 | ||
142 | Development Cost | |
143 | ---------------- | |
882227f1 | 144 | A typical frontend for fast-import tends to weigh in at approximately 200 |
6e411d20 SP |
145 | lines of Perl/Python/Ruby code. Most developers have been able to |
146 | create working importers in just a couple of hours, even though it | |
882227f1 | 147 | is their first exposure to fast-import, and sometimes even to Git. This is |
6e411d20 SP |
148 | an ideal situation, given that most conversion tools are throw-away |
149 | (use once, and never look back). | |
150 | ||
151 | ||
152 | Parallel Operation | |
153 | ------------------ | |
0b444cdb | 154 | Like 'git push' or 'git fetch', imports handled by fast-import are safe to |
6e411d20 | 155 | run alongside parallel `git repack -a -d` or `git gc` invocations, |
0b444cdb | 156 | or any other Git operation (including 'git prune', as loose objects |
882227f1 | 157 | are never used by fast-import). |
6e411d20 | 158 | |
882227f1 SP |
159 | fast-import does not lock the branch or tag refs it is actively importing. |
160 | After the import, during its ref update phase, fast-import tests each | |
7073e69e SP |
161 | existing branch ref to verify the update will be a fast-forward |
162 | update (the commit stored in the ref is contained in the new | |
163 | history of the commit to be written). If the update is not a | |
882227f1 SP |
164 | fast-forward update, fast-import will skip updating that ref and instead |
165 | prints a warning message. fast-import will always attempt to update all | |
7073e69e SP |
166 | branch refs, and does not stop on the first failure. |
167 | ||
6a5d0b0a | 168 | Branch updates can be forced with \--force, but it's recommended that |
c499d768 | 169 | this only be used on an otherwise quiet repository. Using \--force |
7073e69e | 170 | is not necessary for an initial import into an empty repository. |
6e411d20 SP |
171 | |
172 | ||
173 | Technical Discussion | |
174 | -------------------- | |
882227f1 | 175 | fast-import tracks a set of branches in memory. Any branch can be created |
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176 | or modified at any point during the import process by sending a |
177 | `commit` command on the input stream. This design allows a frontend | |
178 | program to process an unlimited number of branches simultaneously, | |
179 | generating commits in the order they are available from the source | |
180 | data. It also simplifies the frontend programs considerably. | |
181 | ||
882227f1 | 182 | fast-import does not use or alter the current working directory, or any |
6e411d20 SP |
183 | file within it. (It does however update the current Git repository, |
184 | as referenced by `GIT_DIR`.) Therefore an import frontend may use | |
185 | the working directory for its own purposes, such as extracting file | |
186 | revisions from the foreign source. This ignorance of the working | |
882227f1 | 187 | directory also allows fast-import to run very quickly, as it does not |
6e411d20 SP |
188 | need to perform any costly file update operations when switching |
189 | between branches. | |
190 | ||
191 | Input Format | |
192 | ------------ | |
193 | With the exception of raw file data (which Git does not interpret) | |
882227f1 | 194 | the fast-import input format is text (ASCII) based. This text based |
6e411d20 SP |
195 | format simplifies development and debugging of frontend programs, |
196 | especially when a higher level language such as Perl, Python or | |
197 | Ruby is being used. | |
198 | ||
882227f1 | 199 | fast-import is very strict about its input. Where we say SP below we mean |
8dc6a373 DB |
200 | *exactly* one space. Likewise LF means one (and only one) linefeed |
201 | and HT one (and only one) horizontal tab. | |
6e411d20 SP |
202 | Supplying additional whitespace characters will cause unexpected |
203 | results, such as branch names or file names with leading or trailing | |
882227f1 | 204 | spaces in their name, or early termination of fast-import when it encounters |
6e411d20 SP |
205 | unexpected input. |
206 | ||
401d53fa SP |
207 | Stream Comments |
208 | ~~~~~~~~~~~~~~~ | |
209 | To aid in debugging frontends fast-import ignores any line that | |
210 | begins with `#` (ASCII pound/hash) up to and including the line | |
211 | ending `LF`. A comment line may contain any sequence of bytes | |
212 | that does not contain an LF and therefore may be used to include | |
213 | any detailed debugging information that might be specific to the | |
214 | frontend and useful when inspecting a fast-import data stream. | |
215 | ||
63e0c8b3 SP |
216 | Date Formats |
217 | ~~~~~~~~~~~~ | |
218 | The following date formats are supported. A frontend should select | |
219 | the format it will use for this import by passing the format name | |
c499d768 | 220 | in the \--date-format=<fmt> command line option. |
63e0c8b3 SP |
221 | |
222 | `raw`:: | |
9b92c82f | 223 | This is the Git native format and is `<time> SP <offutc>`. |
882227f1 | 224 | It is also fast-import's default format, if \--date-format was |
63e0c8b3 SP |
225 | not specified. |
226 | + | |
227 | The time of the event is specified by `<time>` as the number of | |
228 | seconds since the UNIX epoch (midnight, Jan 1, 1970, UTC) and is | |
229 | written as an ASCII decimal integer. | |
230 | + | |
9b92c82f SP |
231 | The local offset is specified by `<offutc>` as a positive or negative |
232 | offset from UTC. For example EST (which is 5 hours behind UTC) | |
233 | would be expressed in `<tz>` by ``-0500'' while UTC is ``+0000''. | |
234 | The local offset does not affect `<time>`; it is used only as an | |
235 | advisement to help formatting routines display the timestamp. | |
63e0c8b3 | 236 | + |
9b92c82f SP |
237 | If the local offset is not available in the source material, use |
238 | ``+0000'', or the most common local offset. For example many | |
63e0c8b3 SP |
239 | organizations have a CVS repository which has only ever been accessed |
240 | by users who are located in the same location and timezone. In this | |
f842fdb0 | 241 | case a reasonable offset from UTC could be assumed. |
63e0c8b3 SP |
242 | + |
243 | Unlike the `rfc2822` format, this format is very strict. Any | |
882227f1 | 244 | variation in formatting will cause fast-import to reject the value. |
63e0c8b3 SP |
245 | |
246 | `rfc2822`:: | |
247 | This is the standard email format as described by RFC 2822. | |
248 | + | |
249 | An example value is ``Tue Feb 6 11:22:18 2007 -0500''. The Git | |
f842fdb0 | 250 | parser is accurate, but a little on the lenient side. It is the |
0b444cdb | 251 | same parser used by 'git am' when applying patches |
63e0c8b3 SP |
252 | received from email. |
253 | + | |
254 | Some malformed strings may be accepted as valid dates. In some of | |
255 | these cases Git will still be able to obtain the correct date from | |
256 | the malformed string. There are also some types of malformed | |
257 | strings which Git will parse wrong, and yet consider valid. | |
258 | Seriously malformed strings will be rejected. | |
259 | + | |
9b92c82f SP |
260 | Unlike the `raw` format above, the timezone/UTC offset information |
261 | contained in an RFC 2822 date string is used to adjust the date | |
262 | value to UTC prior to storage. Therefore it is important that | |
263 | this information be as accurate as possible. | |
264 | + | |
f842fdb0 | 265 | If the source material uses RFC 2822 style dates, |
882227f1 | 266 | the frontend should let fast-import handle the parsing and conversion |
63e0c8b3 SP |
267 | (rather than attempting to do it itself) as the Git parser has |
268 | been well tested in the wild. | |
269 | + | |
270 | Frontends should prefer the `raw` format if the source material | |
f842fdb0 | 271 | already uses UNIX-epoch format, can be coaxed to give dates in that |
02783075 | 272 | format, or its format is easily convertible to it, as there is no |
f842fdb0 | 273 | ambiguity in parsing. |
63e0c8b3 SP |
274 | |
275 | `now`:: | |
276 | Always use the current time and timezone. The literal | |
277 | `now` must always be supplied for `<when>`. | |
278 | + | |
279 | This is a toy format. The current time and timezone of this system | |
280 | is always copied into the identity string at the time it is being | |
882227f1 | 281 | created by fast-import. There is no way to specify a different time or |
63e0c8b3 SP |
282 | timezone. |
283 | + | |
6a5d0b0a | 284 | This particular format is supplied as it's short to implement and |
63e0c8b3 SP |
285 | may be useful to a process that wants to create a new commit |
286 | right now, without needing to use a working directory or | |
0b444cdb | 287 | 'git update-index'. |
63e0c8b3 SP |
288 | + |
289 | If separate `author` and `committer` commands are used in a `commit` | |
290 | the timestamps may not match, as the system clock will be polled | |
291 | twice (once for each command). The only way to ensure that both | |
292 | author and committer identity information has the same timestamp | |
293 | is to omit `author` (thus copying from `committer`) or to use a | |
294 | date format other than `now`. | |
295 | ||
6e411d20 SP |
296 | Commands |
297 | ~~~~~~~~ | |
882227f1 | 298 | fast-import accepts several commands to update the current repository |
6e411d20 SP |
299 | and control the current import process. More detailed discussion |
300 | (with examples) of each command follows later. | |
301 | ||
302 | `commit`:: | |
303 | Creates a new branch or updates an existing branch by | |
304 | creating a new commit and updating the branch to point at | |
305 | the newly created commit. | |
306 | ||
307 | `tag`:: | |
308 | Creates an annotated tag object from an existing commit or | |
309 | branch. Lightweight tags are not supported by this command, | |
310 | as they are not recommended for recording meaningful points | |
311 | in time. | |
312 | ||
313 | `reset`:: | |
314 | Reset an existing branch (or a new branch) to a specific | |
315 | revision. This command must be used to change a branch to | |
316 | a specific revision without making a commit on it. | |
317 | ||
318 | `blob`:: | |
319 | Convert raw file data into a blob, for future use in a | |
320 | `commit` command. This command is optional and is not | |
321 | needed to perform an import. | |
322 | ||
323 | `checkpoint`:: | |
882227f1 | 324 | Forces fast-import to close the current packfile, generate its |
6e411d20 SP |
325 | unique SHA-1 checksum and index, and start a new packfile. |
326 | This command is optional and is not needed to perform | |
327 | an import. | |
328 | ||
ac053c02 SP |
329 | `progress`:: |
330 | Causes fast-import to echo the entire line to its own | |
331 | standard output. This command is optional and is not needed | |
332 | to perform an import. | |
333 | ||
85c62395 DB |
334 | `cat-blob`:: |
335 | Causes fast-import to print a blob in 'cat-file --batch' | |
336 | format to the file descriptor set with `--cat-blob-fd` or | |
337 | `stdout` if unspecified. | |
338 | ||
8dc6a373 DB |
339 | `ls`:: |
340 | Causes fast-import to print a line describing a directory | |
341 | entry in 'ls-tree' format to the file descriptor set with | |
342 | `--cat-blob-fd` or `stdout` if unspecified. | |
343 | ||
f963bd5d SR |
344 | `feature`:: |
345 | Require that fast-import supports the specified feature, or | |
346 | abort if it does not. | |
347 | ||
9c8398f0 SR |
348 | `option`:: |
349 | Specify any of the options listed under OPTIONS that do not | |
350 | change stream semantic to suit the frontend's needs. This | |
351 | command is optional and is not needed to perform an import. | |
352 | ||
6e411d20 SP |
353 | `commit` |
354 | ~~~~~~~~ | |
355 | Create or update a branch with a new commit, recording one logical | |
356 | change to the project. | |
357 | ||
358 | .... | |
359 | 'commit' SP <ref> LF | |
360 | mark? | |
74fbd118 SP |
361 | ('author' (SP <name>)? SP LT <email> GT SP <when> LF)? |
362 | 'committer' (SP <name>)? SP LT <email> GT SP <when> LF | |
6e411d20 SP |
363 | data |
364 | ('from' SP <committish> LF)? | |
365 | ('merge' SP <committish> LF)? | |
a8dd2e7d | 366 | (filemodify | filedelete | filecopy | filerename | filedeleteall | notemodify)* |
1fdb649c | 367 | LF? |
6e411d20 SP |
368 | .... |
369 | ||
370 | where `<ref>` is the name of the branch to make the commit on. | |
371 | Typically branch names are prefixed with `refs/heads/` in | |
372 | Git, so importing the CVS branch symbol `RELENG-1_0` would use | |
373 | `refs/heads/RELENG-1_0` for the value of `<ref>`. The value of | |
374 | `<ref>` must be a valid refname in Git. As `LF` is not valid in | |
375 | a Git refname, no quoting or escaping syntax is supported here. | |
376 | ||
882227f1 | 377 | A `mark` command may optionally appear, requesting fast-import to save a |
6e411d20 SP |
378 | reference to the newly created commit for future use by the frontend |
379 | (see below for format). It is very common for frontends to mark | |
380 | every commit they create, thereby allowing future branch creation | |
381 | from any imported commit. | |
382 | ||
383 | The `data` command following `committer` must supply the commit | |
384 | message (see below for `data` command syntax). To import an empty | |
385 | commit message use a 0 length data. Commit messages are free-form | |
386 | and are not interpreted by Git. Currently they must be encoded in | |
882227f1 | 387 | UTF-8, as fast-import does not permit other encodings to be specified. |
6e411d20 | 388 | |
a8dd2e7d JH |
389 | Zero or more `filemodify`, `filedelete`, `filecopy`, `filerename`, |
390 | `filedeleteall` and `notemodify` commands | |
825769a8 SP |
391 | may be included to update the contents of the branch prior to |
392 | creating the commit. These commands may be supplied in any order. | |
02783075 | 393 | However it is recommended that a `filedeleteall` command precede |
a8dd2e7d JH |
394 | all `filemodify`, `filecopy`, `filerename` and `notemodify` commands in |
395 | the same commit, as `filedeleteall` wipes the branch clean (see below). | |
6e411d20 | 396 | |
1fdb649c SP |
397 | The `LF` after the command is optional (it used to be required). |
398 | ||
6e411d20 SP |
399 | `author` |
400 | ^^^^^^^^ | |
401 | An `author` command may optionally appear, if the author information | |
402 | might differ from the committer information. If `author` is omitted | |
882227f1 | 403 | then fast-import will automatically use the committer's information for |
6e411d20 SP |
404 | the author portion of the commit. See below for a description of |
405 | the fields in `author`, as they are identical to `committer`. | |
406 | ||
407 | `committer` | |
408 | ^^^^^^^^^^^ | |
409 | The `committer` command indicates who made this commit, and when | |
410 | they made it. | |
411 | ||
412 | Here `<name>` is the person's display name (for example | |
413 | ``Com M Itter'') and `<email>` is the person's email address | |
414 | (``cm@example.com''). `LT` and `GT` are the literal less-than (\x3c) | |
415 | and greater-than (\x3e) symbols. These are required to delimit | |
416 | the email address from the other fields in the line. Note that | |
417 | `<name>` is free-form and may contain any sequence of bytes, except | |
418 | `LT` and `LF`. It is typically UTF-8 encoded. | |
419 | ||
63e0c8b3 | 420 | The time of the change is specified by `<when>` using the date format |
c499d768 | 421 | that was selected by the \--date-format=<fmt> command line option. |
63e0c8b3 SP |
422 | See ``Date Formats'' above for the set of supported formats, and |
423 | their syntax. | |
6e411d20 SP |
424 | |
425 | `from` | |
426 | ^^^^^^ | |
ea5e370a SP |
427 | The `from` command is used to specify the commit to initialize |
428 | this branch from. This revision will be the first ancestor of the | |
429 | new commit. | |
430 | ||
431 | Omitting the `from` command in the first commit of a new branch | |
432 | will cause fast-import to create that commit with no ancestor. This | |
433 | tends to be desired only for the initial commit of a project. | |
9b33fa08 EB |
434 | If the frontend creates all files from scratch when making a new |
435 | branch, a `merge` command may be used instead of `from` to start | |
436 | the commit with an empty tree. | |
ea5e370a SP |
437 | Omitting the `from` command on existing branches is usually desired, |
438 | as the current commit on that branch is automatically assumed to | |
439 | be the first ancestor of the new commit. | |
6e411d20 SP |
440 | |
441 | As `LF` is not valid in a Git refname or SHA-1 expression, no | |
442 | quoting or escaping syntax is supported within `<committish>`. | |
443 | ||
444 | Here `<committish>` is any of the following: | |
445 | ||
882227f1 | 446 | * The name of an existing branch already in fast-import's internal branch |
6a5d0b0a | 447 | table. If fast-import doesn't know the name, it's treated as a SHA-1 |
6e411d20 SP |
448 | expression. |
449 | ||
450 | * A mark reference, `:<idnum>`, where `<idnum>` is the mark number. | |
451 | + | |
882227f1 | 452 | The reason fast-import uses `:` to denote a mark reference is this character |
6e411d20 | 453 | is not legal in a Git branch name. The leading `:` makes it easy |
02783075 | 454 | to distinguish between the mark 42 (`:42`) and the branch 42 (`42` |
6e411d20 SP |
455 | or `refs/heads/42`), or an abbreviated SHA-1 which happened to |
456 | consist only of base-10 digits. | |
457 | + | |
458 | Marks must be declared (via `mark`) before they can be used. | |
459 | ||
460 | * A complete 40 byte or abbreviated commit SHA-1 in hex. | |
461 | ||
462 | * Any valid Git SHA-1 expression that resolves to a commit. See | |
9d83e382 | 463 | ``SPECIFYING REVISIONS'' in linkgit:gitrevisions[7] for details. |
6e411d20 SP |
464 | |
465 | The special case of restarting an incremental import from the | |
466 | current branch value should be written as: | |
467 | ---- | |
468 | from refs/heads/branch^0 | |
469 | ---- | |
882227f1 | 470 | The `{caret}0` suffix is necessary as fast-import does not permit a branch to |
6e411d20 | 471 | start from itself, and the branch is created in memory before the |
209f1298 | 472 | `from` command is even read from the input. Adding `{caret}0` will force |
882227f1 | 473 | fast-import to resolve the commit through Git's revision parsing library, |
6e411d20 SP |
474 | rather than its internal branch table, thereby loading in the |
475 | existing value of the branch. | |
476 | ||
477 | `merge` | |
478 | ^^^^^^^ | |
9b33fa08 EB |
479 | Includes one additional ancestor commit. If the `from` command is |
480 | omitted when creating a new branch, the first `merge` commit will be | |
481 | the first ancestor of the current commit, and the branch will start | |
482 | out with no files. An unlimited number of `merge` commands per | |
882227f1 | 483 | commit are permitted by fast-import, thereby establishing an n-way merge. |
6e411d20 SP |
484 | However Git's other tools never create commits with more than 15 |
485 | additional ancestors (forming a 16-way merge). For this reason | |
486 | it is suggested that frontends do not use more than 15 `merge` | |
9b33fa08 | 487 | commands per commit; 16, if starting a new, empty branch. |
6e411d20 SP |
488 | |
489 | Here `<committish>` is any of the commit specification expressions | |
490 | also accepted by `from` (see above). | |
491 | ||
492 | `filemodify` | |
ef94edb5 | 493 | ^^^^^^^^^^^^ |
6e411d20 SP |
494 | Included in a `commit` command to add a new file or change the |
495 | content of an existing file. This command has two different means | |
496 | of specifying the content of the file. | |
497 | ||
498 | External data format:: | |
499 | The data content for the file was already supplied by a prior | |
500 | `blob` command. The frontend just needs to connect it. | |
501 | + | |
502 | .... | |
503 | 'M' SP <mode> SP <dataref> SP <path> LF | |
504 | .... | |
505 | + | |
334fba65 | 506 | Here usually `<dataref>` must be either a mark reference (`:<idnum>`) |
6e411d20 | 507 | set by a prior `blob` command, or a full 40-byte SHA-1 of an |
334fba65 JN |
508 | existing Git blob object. If `<mode>` is `040000`` then |
509 | `<dataref>` must be the full 40-byte SHA-1 of an existing | |
510 | Git tree object or a mark reference set with `--import-marks`. | |
6e411d20 SP |
511 | |
512 | Inline data format:: | |
513 | The data content for the file has not been supplied yet. | |
514 | The frontend wants to supply it as part of this modify | |
515 | command. | |
516 | + | |
517 | .... | |
518 | 'M' SP <mode> SP 'inline' SP <path> LF | |
519 | data | |
520 | .... | |
521 | + | |
522 | See below for a detailed description of the `data` command. | |
523 | ||
524 | In both formats `<mode>` is the type of file entry, specified | |
525 | in octal. Git only supports the following modes: | |
526 | ||
527 | * `100644` or `644`: A normal (not-executable) file. The majority | |
528 | of files in most projects use this mode. If in doubt, this is | |
529 | what you want. | |
530 | * `100755` or `755`: A normal, but executable, file. | |
9981b6d9 | 531 | * `120000`: A symlink, the content of the file will be the link target. |
03db4525 AG |
532 | * `160000`: A gitlink, SHA-1 of the object refers to a commit in |
533 | another repository. Git links can only be specified by SHA or through | |
534 | a commit mark. They are used to implement submodules. | |
334fba65 JN |
535 | * `040000`: A subdirectory. Subdirectories can only be specified by |
536 | SHA or through a tree mark set with `--import-marks`. | |
6e411d20 SP |
537 | |
538 | In both formats `<path>` is the complete path of the file to be added | |
539 | (if not already existing) or modified (if already existing). | |
540 | ||
c4431d38 | 541 | A `<path>` string must use UNIX-style directory separators (forward |
6e411d20 SP |
542 | slash `/`), may contain any byte other than `LF`, and must not |
543 | start with double quote (`"`). | |
544 | ||
545 | If an `LF` or double quote must be encoded into `<path>` shell-style | |
546 | quoting should be used, e.g. `"path/with\n and \" in it"`. | |
547 | ||
02783075 | 548 | The value of `<path>` must be in canonical form. That is it must not: |
6e411d20 SP |
549 | |
550 | * contain an empty directory component (e.g. `foo//bar` is invalid), | |
c4431d38 JK |
551 | * end with a directory separator (e.g. `foo/` is invalid), |
552 | * start with a directory separator (e.g. `/foo` is invalid), | |
6e411d20 SP |
553 | * contain the special component `.` or `..` (e.g. `foo/./bar` and |
554 | `foo/../bar` are invalid). | |
555 | ||
e5959106 JN |
556 | The root of the tree can be represented by an empty string as `<path>`. |
557 | ||
6e411d20 SP |
558 | It is recommended that `<path>` always be encoded using UTF-8. |
559 | ||
6e411d20 | 560 | `filedelete` |
ef94edb5 | 561 | ^^^^^^^^^^^^ |
512e44b2 SP |
562 | Included in a `commit` command to remove a file or recursively |
563 | delete an entire directory from the branch. If the file or directory | |
564 | removal makes its parent directory empty, the parent directory will | |
6e411d20 SP |
565 | be automatically removed too. This cascades up the tree until the |
566 | first non-empty directory or the root is reached. | |
567 | ||
568 | .... | |
569 | 'D' SP <path> LF | |
570 | .... | |
571 | ||
512e44b2 SP |
572 | here `<path>` is the complete path of the file or subdirectory to |
573 | be removed from the branch. | |
6e411d20 SP |
574 | See `filemodify` above for a detailed description of `<path>`. |
575 | ||
b6f3481b SP |
576 | `filecopy` |
577 | ^^^^^^^^^^^^ | |
578 | Recursively copies an existing file or subdirectory to a different | |
579 | location within the branch. The existing file or directory must | |
580 | exist. If the destination exists it will be completely replaced | |
581 | by the content copied from the source. | |
582 | ||
583 | .... | |
584 | 'C' SP <path> SP <path> LF | |
585 | .... | |
586 | ||
587 | here the first `<path>` is the source location and the second | |
588 | `<path>` is the destination. See `filemodify` above for a detailed | |
589 | description of what `<path>` may look like. To use a source path | |
590 | that contains SP the path must be quoted. | |
591 | ||
592 | A `filecopy` command takes effect immediately. Once the source | |
593 | location has been copied to the destination any future commands | |
594 | applied to the source location will not impact the destination of | |
595 | the copy. | |
596 | ||
f39a946a SP |
597 | `filerename` |
598 | ^^^^^^^^^^^^ | |
599 | Renames an existing file or subdirectory to a different location | |
600 | within the branch. The existing file or directory must exist. If | |
601 | the destination exists it will be replaced by the source directory. | |
602 | ||
603 | .... | |
604 | 'R' SP <path> SP <path> LF | |
605 | .... | |
606 | ||
607 | here the first `<path>` is the source location and the second | |
608 | `<path>` is the destination. See `filemodify` above for a detailed | |
609 | description of what `<path>` may look like. To use a source path | |
610 | that contains SP the path must be quoted. | |
611 | ||
612 | A `filerename` command takes effect immediately. Once the source | |
613 | location has been renamed to the destination any future commands | |
614 | applied to the source location will create new files there and not | |
615 | impact the destination of the rename. | |
616 | ||
b6f3481b SP |
617 | Note that a `filerename` is the same as a `filecopy` followed by a |
618 | `filedelete` of the source location. There is a slight performance | |
619 | advantage to using `filerename`, but the advantage is so small | |
620 | that it is never worth trying to convert a delete/add pair in | |
621 | source material into a rename for fast-import. This `filerename` | |
622 | command is provided just to simplify frontends that already have | |
623 | rename information and don't want bother with decomposing it into a | |
624 | `filecopy` followed by a `filedelete`. | |
625 | ||
825769a8 SP |
626 | `filedeleteall` |
627 | ^^^^^^^^^^^^^^^ | |
628 | Included in a `commit` command to remove all files (and also all | |
629 | directories) from the branch. This command resets the internal | |
630 | branch structure to have no files in it, allowing the frontend | |
631 | to subsequently add all interesting files from scratch. | |
632 | ||
633 | .... | |
634 | 'deleteall' LF | |
635 | .... | |
636 | ||
637 | This command is extremely useful if the frontend does not know | |
638 | (or does not care to know) what files are currently on the branch, | |
639 | and therefore cannot generate the proper `filedelete` commands to | |
640 | update the content. | |
641 | ||
642 | Issuing a `filedeleteall` followed by the needed `filemodify` | |
643 | commands to set the correct content will produce the same results | |
644 | as sending only the needed `filemodify` and `filedelete` commands. | |
882227f1 | 645 | The `filedeleteall` approach may however require fast-import to use slightly |
825769a8 SP |
646 | more memory per active branch (less than 1 MiB for even most large |
647 | projects); so frontends that can easily obtain only the affected | |
648 | paths for a commit are encouraged to do so. | |
649 | ||
a8dd2e7d JH |
650 | `notemodify` |
651 | ^^^^^^^^^^^^ | |
652 | Included in a `commit` command to add a new note (annotating a given | |
653 | commit) or change the content of an existing note. This command has | |
654 | two different means of specifying the content of the note. | |
655 | ||
656 | External data format:: | |
657 | The data content for the note was already supplied by a prior | |
658 | `blob` command. The frontend just needs to connect it to the | |
659 | commit that is to be annotated. | |
660 | + | |
661 | .... | |
662 | 'N' SP <dataref> SP <committish> LF | |
663 | .... | |
664 | + | |
665 | Here `<dataref>` can be either a mark reference (`:<idnum>`) | |
666 | set by a prior `blob` command, or a full 40-byte SHA-1 of an | |
667 | existing Git blob object. | |
668 | ||
669 | Inline data format:: | |
670 | The data content for the note has not been supplied yet. | |
671 | The frontend wants to supply it as part of this modify | |
672 | command. | |
673 | + | |
674 | .... | |
675 | 'N' SP 'inline' SP <committish> LF | |
676 | data | |
677 | .... | |
678 | + | |
679 | See below for a detailed description of the `data` command. | |
680 | ||
681 | In both formats `<committish>` is any of the commit specification | |
682 | expressions also accepted by `from` (see above). | |
683 | ||
6e411d20 SP |
684 | `mark` |
685 | ~~~~~~ | |
882227f1 | 686 | Arranges for fast-import to save a reference to the current object, allowing |
6e411d20 SP |
687 | the frontend to recall this object at a future point in time, without |
688 | knowing its SHA-1. Here the current object is the object creation | |
689 | command the `mark` command appears within. This can be `commit`, | |
690 | `tag`, and `blob`, but `commit` is the most common usage. | |
691 | ||
692 | .... | |
693 | 'mark' SP ':' <idnum> LF | |
694 | .... | |
695 | ||
696 | where `<idnum>` is the number assigned by the frontend to this mark. | |
ef94edb5 SP |
697 | The value of `<idnum>` is expressed as an ASCII decimal integer. |
698 | The value 0 is reserved and cannot be used as | |
6e411d20 SP |
699 | a mark. Only values greater than or equal to 1 may be used as marks. |
700 | ||
701 | New marks are created automatically. Existing marks can be moved | |
702 | to another object simply by reusing the same `<idnum>` in another | |
703 | `mark` command. | |
704 | ||
705 | `tag` | |
706 | ~~~~~ | |
707 | Creates an annotated tag referring to a specific commit. To create | |
708 | lightweight (non-annotated) tags see the `reset` command below. | |
709 | ||
710 | .... | |
711 | 'tag' SP <name> LF | |
712 | 'from' SP <committish> LF | |
74fbd118 | 713 | 'tagger' (SP <name>)? SP LT <email> GT SP <when> LF |
6e411d20 | 714 | data |
6e411d20 SP |
715 | .... |
716 | ||
717 | where `<name>` is the name of the tag to create. | |
718 | ||
719 | Tag names are automatically prefixed with `refs/tags/` when stored | |
720 | in Git, so importing the CVS branch symbol `RELENG-1_0-FINAL` would | |
882227f1 | 721 | use just `RELENG-1_0-FINAL` for `<name>`, and fast-import will write the |
6e411d20 SP |
722 | corresponding ref as `refs/tags/RELENG-1_0-FINAL`. |
723 | ||
724 | The value of `<name>` must be a valid refname in Git and therefore | |
725 | may contain forward slashes. As `LF` is not valid in a Git refname, | |
726 | no quoting or escaping syntax is supported here. | |
727 | ||
728 | The `from` command is the same as in the `commit` command; see | |
729 | above for details. | |
730 | ||
731 | The `tagger` command uses the same format as `committer` within | |
732 | `commit`; again see above for details. | |
733 | ||
734 | The `data` command following `tagger` must supply the annotated tag | |
735 | message (see below for `data` command syntax). To import an empty | |
736 | tag message use a 0 length data. Tag messages are free-form and are | |
737 | not interpreted by Git. Currently they must be encoded in UTF-8, | |
882227f1 | 738 | as fast-import does not permit other encodings to be specified. |
6e411d20 | 739 | |
882227f1 | 740 | Signing annotated tags during import from within fast-import is not |
6e411d20 SP |
741 | supported. Trying to include your own PGP/GPG signature is not |
742 | recommended, as the frontend does not (easily) have access to the | |
743 | complete set of bytes which normally goes into such a signature. | |
882227f1 | 744 | If signing is required, create lightweight tags from within fast-import with |
6e411d20 | 745 | `reset`, then create the annotated versions of those tags offline |
0b444cdb | 746 | with the standard 'git tag' process. |
6e411d20 SP |
747 | |
748 | `reset` | |
749 | ~~~~~~~ | |
750 | Creates (or recreates) the named branch, optionally starting from | |
751 | a specific revision. The reset command allows a frontend to issue | |
752 | a new `from` command for an existing branch, or to create a new | |
753 | branch from an existing commit without creating a new commit. | |
754 | ||
755 | .... | |
756 | 'reset' SP <ref> LF | |
757 | ('from' SP <committish> LF)? | |
1fdb649c | 758 | LF? |
6e411d20 SP |
759 | .... |
760 | ||
761 | For a detailed description of `<ref>` and `<committish>` see above | |
762 | under `commit` and `from`. | |
763 | ||
1fdb649c SP |
764 | The `LF` after the command is optional (it used to be required). |
765 | ||
6e411d20 SP |
766 | The `reset` command can also be used to create lightweight |
767 | (non-annotated) tags. For example: | |
768 | ||
769 | ==== | |
770 | reset refs/tags/938 | |
771 | from :938 | |
772 | ==== | |
773 | ||
774 | would create the lightweight tag `refs/tags/938` referring to | |
775 | whatever commit mark `:938` references. | |
776 | ||
777 | `blob` | |
778 | ~~~~~~ | |
779 | Requests writing one file revision to the packfile. The revision | |
780 | is not connected to any commit; this connection must be formed in | |
781 | a subsequent `commit` command by referencing the blob through an | |
782 | assigned mark. | |
783 | ||
784 | .... | |
785 | 'blob' LF | |
786 | mark? | |
787 | data | |
788 | .... | |
789 | ||
790 | The mark command is optional here as some frontends have chosen | |
791 | to generate the Git SHA-1 for the blob on their own, and feed that | |
6a5d0b0a | 792 | directly to `commit`. This is typically more work than it's worth |
6e411d20 SP |
793 | however, as marks are inexpensive to store and easy to use. |
794 | ||
795 | `data` | |
796 | ~~~~~~ | |
797 | Supplies raw data (for use as blob/file content, commit messages, or | |
882227f1 | 798 | annotated tag messages) to fast-import. Data can be supplied using an exact |
6e411d20 SP |
799 | byte count or delimited with a terminating line. Real frontends |
800 | intended for production-quality conversions should always use the | |
801 | exact byte count format, as it is more robust and performs better. | |
882227f1 | 802 | The delimited format is intended primarily for testing fast-import. |
6e411d20 | 803 | |
401d53fa SP |
804 | Comment lines appearing within the `<raw>` part of `data` commands |
805 | are always taken to be part of the body of the data and are therefore | |
806 | never ignored by fast-import. This makes it safe to import any | |
807 | file/message content whose lines might start with `#`. | |
808 | ||
ef94edb5 SP |
809 | Exact byte count format:: |
810 | The frontend must specify the number of bytes of data. | |
811 | + | |
6e411d20 SP |
812 | .... |
813 | 'data' SP <count> LF | |
2c570cde | 814 | <raw> LF? |
6e411d20 | 815 | .... |
ef94edb5 | 816 | + |
6e411d20 | 817 | where `<count>` is the exact number of bytes appearing within |
ef94edb5 SP |
818 | `<raw>`. The value of `<count>` is expressed as an ASCII decimal |
819 | integer. The `LF` on either side of `<raw>` is not | |
6e411d20 | 820 | included in `<count>` and will not be included in the imported data. |
2c570cde SP |
821 | + |
822 | The `LF` after `<raw>` is optional (it used to be required) but | |
823 | recommended. Always including it makes debugging a fast-import | |
824 | stream easier as the next command always starts in column 0 | |
825 | of the next line, even if `<raw>` did not end with an `LF`. | |
6e411d20 | 826 | |
ef94edb5 SP |
827 | Delimited format:: |
828 | A delimiter string is used to mark the end of the data. | |
882227f1 | 829 | fast-import will compute the length by searching for the delimiter. |
02783075 | 830 | This format is primarily useful for testing and is not |
ef94edb5 SP |
831 | recommended for real data. |
832 | + | |
6e411d20 SP |
833 | .... |
834 | 'data' SP '<<' <delim> LF | |
835 | <raw> LF | |
836 | <delim> LF | |
2c570cde | 837 | LF? |
6e411d20 | 838 | .... |
ef94edb5 | 839 | + |
6e411d20 SP |
840 | where `<delim>` is the chosen delimiter string. The string `<delim>` |
841 | must not appear on a line by itself within `<raw>`, as otherwise | |
882227f1 | 842 | fast-import will think the data ends earlier than it really does. The `LF` |
6e411d20 SP |
843 | immediately trailing `<raw>` is part of `<raw>`. This is one of |
844 | the limitations of the delimited format, it is impossible to supply | |
845 | a data chunk which does not have an LF as its last byte. | |
2c570cde SP |
846 | + |
847 | The `LF` after `<delim> LF` is optional (it used to be required). | |
6e411d20 SP |
848 | |
849 | `checkpoint` | |
850 | ~~~~~~~~~~~~ | |
882227f1 | 851 | Forces fast-import to close the current packfile, start a new one, and to |
820b9310 | 852 | save out all current branch refs, tags and marks. |
6e411d20 SP |
853 | |
854 | .... | |
855 | 'checkpoint' LF | |
1fdb649c | 856 | LF? |
6e411d20 SP |
857 | .... |
858 | ||
882227f1 | 859 | Note that fast-import automatically switches packfiles when the current |
820b9310 | 860 | packfile reaches \--max-pack-size, or 4 GiB, whichever limit is |
882227f1 | 861 | smaller. During an automatic packfile switch fast-import does not update |
820b9310 SP |
862 | the branch refs, tags or marks. |
863 | ||
864 | As a `checkpoint` can require a significant amount of CPU time and | |
865 | disk IO (to compute the overall pack SHA-1 checksum, generate the | |
866 | corresponding index file, and update the refs) it can easily take | |
867 | several minutes for a single `checkpoint` command to complete. | |
868 | ||
869 | Frontends may choose to issue checkpoints during extremely large | |
870 | and long running imports, or when they need to allow another Git | |
871 | process access to a branch. However given that a 30 GiB Subversion | |
882227f1 | 872 | repository can be loaded into Git through fast-import in about 3 hours, |
820b9310 SP |
873 | explicit checkpointing may not be necessary. |
874 | ||
1fdb649c | 875 | The `LF` after the command is optional (it used to be required). |
820b9310 | 876 | |
ac053c02 SP |
877 | `progress` |
878 | ~~~~~~~~~~ | |
879 | Causes fast-import to print the entire `progress` line unmodified to | |
880 | its standard output channel (file descriptor 1) when the command is | |
881 | processed from the input stream. The command otherwise has no impact | |
882 | on the current import, or on any of fast-import's internal state. | |
883 | ||
884 | .... | |
885 | 'progress' SP <any> LF | |
886 | LF? | |
887 | .... | |
888 | ||
889 | The `<any>` part of the command may contain any sequence of bytes | |
890 | that does not contain `LF`. The `LF` after the command is optional. | |
891 | Callers may wish to process the output through a tool such as sed to | |
892 | remove the leading part of the line, for example: | |
893 | ||
894 | ==== | |
b1889c36 | 895 | frontend | git fast-import | sed 's/^progress //' |
ac053c02 SP |
896 | ==== |
897 | ||
898 | Placing a `progress` command immediately after a `checkpoint` will | |
899 | inform the reader when the `checkpoint` has been completed and it | |
900 | can safely access the refs that fast-import updated. | |
901 | ||
85c62395 DB |
902 | `cat-blob` |
903 | ~~~~~~~~~~ | |
904 | Causes fast-import to print a blob to a file descriptor previously | |
905 | arranged with the `--cat-blob-fd` argument. The command otherwise | |
906 | has no impact on the current import; its main purpose is to | |
907 | retrieve blobs that may be in fast-import's memory but not | |
908 | accessible from the target repository. | |
909 | ||
910 | .... | |
911 | 'cat-blob' SP <dataref> LF | |
912 | .... | |
913 | ||
914 | The `<dataref>` can be either a mark reference (`:<idnum>`) | |
915 | set previously or a full 40-byte SHA-1 of a Git blob, preexisting or | |
916 | ready to be written. | |
917 | ||
898243b8 | 918 | Output uses the same format as `git cat-file --batch`: |
85c62395 DB |
919 | |
920 | ==== | |
921 | <sha1> SP 'blob' SP <size> LF | |
922 | <contents> LF | |
923 | ==== | |
924 | ||
777f80d7 JN |
925 | This command can be used anywhere in the stream that comments are |
926 | accepted. In particular, the `cat-blob` command can be used in the | |
927 | middle of a commit but not in the middle of a `data` command. | |
928 | ||
8dc6a373 DB |
929 | `ls` |
930 | ~~~~ | |
931 | Prints information about the object at a path to a file descriptor | |
932 | previously arranged with the `--cat-blob-fd` argument. This allows | |
933 | printing a blob from the active commit (with `cat-blob`) or copying a | |
934 | blob or tree from a previous commit for use in the current one (with | |
935 | `filemodify`). | |
936 | ||
937 | The `ls` command can be used anywhere in the stream that comments are | |
938 | accepted, including the middle of a commit. | |
939 | ||
940 | Reading from the active commit:: | |
941 | This form can only be used in the middle of a `commit`. | |
942 | The path names a directory entry within fast-import's | |
943 | active commit. The path must be quoted in this case. | |
944 | + | |
945 | .... | |
946 | 'ls' SP <path> LF | |
947 | .... | |
948 | ||
949 | Reading from a named tree:: | |
950 | The `<dataref>` can be a mark reference (`:<idnum>`) or the | |
951 | full 40-byte SHA-1 of a Git tag, commit, or tree object, | |
952 | preexisting or waiting to be written. | |
953 | The path is relative to the top level of the tree | |
954 | named by `<dataref>`. | |
955 | + | |
956 | .... | |
957 | 'ls' SP <dataref> SP <path> LF | |
958 | .... | |
959 | ||
960 | See `filemodify` above for a detailed description of `<path>`. | |
961 | ||
962 | Output uses the same format as `git ls-tree <tree> {litdd} <path>`: | |
963 | ||
964 | ==== | |
965 | <mode> SP ('blob' | 'tree' | 'commit') SP <dataref> HT <path> LF | |
966 | ==== | |
967 | ||
968 | The <dataref> represents the blob, tree, or commit object at <path> | |
969 | and can be used in later 'cat-blob', 'filemodify', or 'ls' commands. | |
970 | ||
971 | If there is no file or subtree at that path, 'git fast-import' will | |
972 | instead report | |
973 | ||
974 | ==== | |
975 | missing SP <path> LF | |
976 | ==== | |
977 | ||
f963bd5d SR |
978 | `feature` |
979 | ~~~~~~~~~ | |
980 | Require that fast-import supports the specified feature, or abort if | |
981 | it does not. | |
982 | ||
983 | .... | |
4980fffb | 984 | 'feature' SP <feature> ('=' <argument>)? LF |
f963bd5d SR |
985 | .... |
986 | ||
4980fffb | 987 | The <feature> part of the command may be any one of the following: |
f963bd5d | 988 | |
4980fffb JN |
989 | date-format:: |
990 | export-marks:: | |
991 | relative-marks:: | |
992 | no-relative-marks:: | |
993 | force:: | |
994 | Act as though the corresponding command-line option with | |
995 | a leading '--' was passed on the command line | |
996 | (see OPTIONS, above). | |
f963bd5d | 997 | |
4980fffb JN |
998 | import-marks:: |
999 | Like --import-marks except in two respects: first, only one | |
1000 | "feature import-marks" command is allowed per stream; | |
1001 | second, an --import-marks= command-line option overrides | |
1002 | any "feature import-marks" command in the stream. | |
f963bd5d | 1003 | |
85c62395 | 1004 | cat-blob:: |
8dc6a373 DB |
1005 | ls:: |
1006 | Require that the backend support the 'cat-blob' or 'ls' command. | |
1007 | Versions of fast-import not supporting the specified command | |
1008 | will exit with a message indicating so. | |
85c62395 DB |
1009 | This lets the import error out early with a clear message, |
1010 | rather than wasting time on the early part of an import | |
1011 | before the unsupported command is detected. | |
081751c8 | 1012 | |
547e8b92 JN |
1013 | notes:: |
1014 | Require that the backend support the 'notemodify' (N) | |
1015 | subcommand to the 'commit' command. | |
1016 | Versions of fast-import not supporting notes will exit | |
1017 | with a message indicating so. | |
1018 | ||
a8e4a594 | 1019 | |
9c8398f0 SR |
1020 | `option` |
1021 | ~~~~~~~~ | |
1022 | Processes the specified option so that git fast-import behaves in a | |
1023 | way that suits the frontend's needs. | |
1024 | Note that options specified by the frontend are overridden by any | |
1025 | options the user may specify to git fast-import itself. | |
1026 | ||
1027 | .... | |
1028 | 'option' SP <option> LF | |
1029 | .... | |
1030 | ||
1031 | The `<option>` part of the command may contain any of the options | |
1032 | listed in the OPTIONS section that do not change import semantics, | |
1033 | without the leading '--' and is treated in the same way. | |
1034 | ||
1035 | Option commands must be the first commands on the input (not counting | |
1036 | feature commands), to give an option command after any non-option | |
1037 | command is an error. | |
1038 | ||
1039 | The following commandline options change import semantics and may therefore | |
1040 | not be passed as option: | |
1041 | ||
1042 | * date-format | |
1043 | * import-marks | |
1044 | * export-marks | |
85c62395 | 1045 | * cat-blob-fd |
9c8398f0 SR |
1046 | * force |
1047 | ||
e7e5170f SP |
1048 | Crash Reports |
1049 | ------------- | |
1050 | If fast-import is supplied invalid input it will terminate with a | |
1051 | non-zero exit status and create a crash report in the top level of | |
1052 | the Git repository it was importing into. Crash reports contain | |
1053 | a snapshot of the internal fast-import state as well as the most | |
1054 | recent commands that lead up to the crash. | |
1055 | ||
1056 | All recent commands (including stream comments, file changes and | |
1057 | progress commands) are shown in the command history within the crash | |
1058 | report, but raw file data and commit messages are excluded from the | |
1059 | crash report. This exclusion saves space within the report file | |
1060 | and reduces the amount of buffering that fast-import must perform | |
1061 | during execution. | |
1062 | ||
1063 | After writing a crash report fast-import will close the current | |
1064 | packfile and export the marks table. This allows the frontend | |
1065 | developer to inspect the repository state and resume the import from | |
1066 | the point where it crashed. The modified branches and tags are not | |
1067 | updated during a crash, as the import did not complete successfully. | |
1068 | Branch and tag information can be found in the crash report and | |
1069 | must be applied manually if the update is needed. | |
1070 | ||
1071 | An example crash: | |
1072 | ||
1073 | ==== | |
1074 | $ cat >in <<END_OF_INPUT | |
1075 | # my very first test commit | |
1076 | commit refs/heads/master | |
1077 | committer Shawn O. Pearce <spearce> 19283 -0400 | |
1078 | # who is that guy anyway? | |
1079 | data <<EOF | |
1080 | this is my commit | |
1081 | EOF | |
1082 | M 644 inline .gitignore | |
1083 | data <<EOF | |
1084 | .gitignore | |
1085 | EOF | |
1086 | M 777 inline bob | |
1087 | END_OF_INPUT | |
1088 | ||
b1889c36 | 1089 | $ git fast-import <in |
e7e5170f SP |
1090 | fatal: Corrupt mode: M 777 inline bob |
1091 | fast-import: dumping crash report to .git/fast_import_crash_8434 | |
1092 | ||
1093 | $ cat .git/fast_import_crash_8434 | |
1094 | fast-import crash report: | |
1095 | fast-import process: 8434 | |
1096 | parent process : 1391 | |
1097 | at Sat Sep 1 00:58:12 2007 | |
1098 | ||
1099 | fatal: Corrupt mode: M 777 inline bob | |
1100 | ||
1101 | Most Recent Commands Before Crash | |
1102 | --------------------------------- | |
1103 | # my very first test commit | |
1104 | commit refs/heads/master | |
1105 | committer Shawn O. Pearce <spearce> 19283 -0400 | |
1106 | # who is that guy anyway? | |
1107 | data <<EOF | |
1108 | M 644 inline .gitignore | |
1109 | data <<EOF | |
1110 | * M 777 inline bob | |
1111 | ||
1112 | Active Branch LRU | |
1113 | ----------------- | |
1114 | active_branches = 1 cur, 5 max | |
1115 | ||
1116 | pos clock name | |
1117 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1118 | 1) 0 refs/heads/master | |
1119 | ||
1120 | Inactive Branches | |
1121 | ----------------- | |
1122 | refs/heads/master: | |
1123 | status : active loaded dirty | |
1124 | tip commit : 0000000000000000000000000000000000000000 | |
1125 | old tree : 0000000000000000000000000000000000000000 | |
1126 | cur tree : 0000000000000000000000000000000000000000 | |
1127 | commit clock: 0 | |
1128 | last pack : | |
1129 | ||
1130 | ||
1131 | ------------------- | |
1132 | END OF CRASH REPORT | |
1133 | ==== | |
1134 | ||
bdd9f424 SP |
1135 | Tips and Tricks |
1136 | --------------- | |
1137 | The following tips and tricks have been collected from various | |
882227f1 | 1138 | users of fast-import, and are offered here as suggestions. |
bdd9f424 SP |
1139 | |
1140 | Use One Mark Per Commit | |
1141 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1142 | When doing a repository conversion, use a unique mark per commit | |
1143 | (`mark :<n>`) and supply the \--export-marks option on the command | |
882227f1 | 1144 | line. fast-import will dump a file which lists every mark and the Git |
bdd9f424 SP |
1145 | object SHA-1 that corresponds to it. If the frontend can tie |
1146 | the marks back to the source repository, it is easy to verify the | |
1147 | accuracy and completeness of the import by comparing each Git | |
1148 | commit to the corresponding source revision. | |
1149 | ||
1150 | Coming from a system such as Perforce or Subversion this should be | |
882227f1 | 1151 | quite simple, as the fast-import mark can also be the Perforce changeset |
bdd9f424 SP |
1152 | number or the Subversion revision number. |
1153 | ||
1154 | Freely Skip Around Branches | |
1155 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1156 | Don't bother trying to optimize the frontend to stick to one branch | |
1157 | at a time during an import. Although doing so might be slightly | |
882227f1 | 1158 | faster for fast-import, it tends to increase the complexity of the frontend |
bdd9f424 SP |
1159 | code considerably. |
1160 | ||
882227f1 | 1161 | The branch LRU builtin to fast-import tends to behave very well, and the |
bdd9f424 SP |
1162 | cost of activating an inactive branch is so low that bouncing around |
1163 | between branches has virtually no impact on import performance. | |
1164 | ||
c7346156 SP |
1165 | Handling Renames |
1166 | ~~~~~~~~~~~~~~~~ | |
1167 | When importing a renamed file or directory, simply delete the old | |
1168 | name(s) and modify the new name(s) during the corresponding commit. | |
1169 | Git performs rename detection after-the-fact, rather than explicitly | |
1170 | during a commit. | |
1171 | ||
bdd9f424 SP |
1172 | Use Tag Fixup Branches |
1173 | ~~~~~~~~~~~~~~~~~~~~~~ | |
1174 | Some other SCM systems let the user create a tag from multiple | |
1175 | files which are not from the same commit/changeset. Or to create | |
1176 | tags which are a subset of the files available in the repository. | |
1177 | ||
1178 | Importing these tags as-is in Git is impossible without making at | |
1179 | least one commit which ``fixes up'' the files to match the content | |
882227f1 | 1180 | of the tag. Use fast-import's `reset` command to reset a dummy branch |
bdd9f424 SP |
1181 | outside of your normal branch space to the base commit for the tag, |
1182 | then commit one or more file fixup commits, and finally tag the | |
1183 | dummy branch. | |
1184 | ||
1185 | For example since all normal branches are stored under `refs/heads/` | |
1186 | name the tag fixup branch `TAG_FIXUP`. This way it is impossible for | |
1187 | the fixup branch used by the importer to have namespace conflicts | |
1188 | with real branches imported from the source (the name `TAG_FIXUP` | |
1189 | is not `refs/heads/TAG_FIXUP`). | |
1190 | ||
1191 | When committing fixups, consider using `merge` to connect the | |
1192 | commit(s) which are supplying file revisions to the fixup branch. | |
0b444cdb | 1193 | Doing so will allow tools such as 'git blame' to track |
bdd9f424 SP |
1194 | through the real commit history and properly annotate the source |
1195 | files. | |
1196 | ||
882227f1 | 1197 | After fast-import terminates the frontend will need to do `rm .git/TAG_FIXUP` |
bdd9f424 SP |
1198 | to remove the dummy branch. |
1199 | ||
1200 | Import Now, Repack Later | |
1201 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
882227f1 | 1202 | As soon as fast-import completes the Git repository is completely valid |
02783075 | 1203 | and ready for use. Typically this takes only a very short time, |
bdd9f424 SP |
1204 | even for considerably large projects (100,000+ commits). |
1205 | ||
1206 | However repacking the repository is necessary to improve data | |
1207 | locality and access performance. It can also take hours on extremely | |
1208 | large projects (especially if -f and a large \--window parameter is | |
1209 | used). Since repacking is safe to run alongside readers and writers, | |
1210 | run the repack in the background and let it finish when it finishes. | |
1211 | There is no reason to wait to explore your new Git project! | |
1212 | ||
1213 | If you choose to wait for the repack, don't try to run benchmarks | |
882227f1 | 1214 | or performance tests until repacking is completed. fast-import outputs |
bdd9f424 SP |
1215 | suboptimal packfiles that are simply never seen in real use |
1216 | situations. | |
1217 | ||
1218 | Repacking Historical Data | |
1219 | ~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1220 | If you are repacking very old imported data (e.g. older than the | |
1221 | last year), consider expending some extra CPU time and supplying | |
0b444cdb | 1222 | \--window=50 (or higher) when you run 'git repack'. |
bdd9f424 SP |
1223 | This will take longer, but will also produce a smaller packfile. |
1224 | You only need to expend the effort once, and everyone using your | |
1225 | project will benefit from the smaller repository. | |
1226 | ||
ac053c02 SP |
1227 | Include Some Progress Messages |
1228 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1229 | Every once in a while have your frontend emit a `progress` message | |
1230 | to fast-import. The contents of the messages are entirely free-form, | |
1231 | so one suggestion would be to output the current month and year | |
1232 | each time the current commit date moves into the next month. | |
1233 | Your users will feel better knowing how much of the data stream | |
1234 | has been processed. | |
1235 | ||
bdd9f424 | 1236 | |
6e411d20 SP |
1237 | Packfile Optimization |
1238 | --------------------- | |
882227f1 | 1239 | When packing a blob fast-import always attempts to deltify against the last |
6e411d20 SP |
1240 | blob written. Unless specifically arranged for by the frontend, |
1241 | this will probably not be a prior version of the same file, so the | |
1242 | generated delta will not be the smallest possible. The resulting | |
1243 | packfile will be compressed, but will not be optimal. | |
1244 | ||
1245 | Frontends which have efficient access to all revisions of a | |
1246 | single file (for example reading an RCS/CVS ,v file) can choose | |
1247 | to supply all revisions of that file as a sequence of consecutive | |
882227f1 | 1248 | `blob` commands. This allows fast-import to deltify the different file |
6e411d20 SP |
1249 | revisions against each other, saving space in the final packfile. |
1250 | Marks can be used to later identify individual file revisions during | |
1251 | a sequence of `commit` commands. | |
1252 | ||
882227f1 SP |
1253 | The packfile(s) created by fast-import do not encourage good disk access |
1254 | patterns. This is caused by fast-import writing the data in the order | |
6e411d20 SP |
1255 | it is received on standard input, while Git typically organizes |
1256 | data within packfiles to make the most recent (current tip) data | |
1257 | appear before historical data. Git also clusters commits together, | |
1258 | speeding up revision traversal through better cache locality. | |
1259 | ||
1260 | For this reason it is strongly recommended that users repack the | |
882227f1 | 1261 | repository with `git repack -a -d` after fast-import completes, allowing |
6e411d20 SP |
1262 | Git to reorganize the packfiles for faster data access. If blob |
1263 | deltas are suboptimal (see above) then also adding the `-f` option | |
1264 | to force recomputation of all deltas can significantly reduce the | |
1265 | final packfile size (30-50% smaller can be quite typical). | |
1266 | ||
bdd9f424 | 1267 | |
6e411d20 SP |
1268 | Memory Utilization |
1269 | ------------------ | |
882227f1 | 1270 | There are a number of factors which affect how much memory fast-import |
6e411d20 | 1271 | requires to perform an import. Like critical sections of core |
02783075 BH |
1272 | Git, fast-import uses its own memory allocators to amortize any overheads |
1273 | associated with malloc. In practice fast-import tends to amortize any | |
6e411d20 SP |
1274 | malloc overheads to 0, due to its use of large block allocations. |
1275 | ||
1276 | per object | |
1277 | ~~~~~~~~~~ | |
882227f1 | 1278 | fast-import maintains an in-memory structure for every object written in |
6e411d20 SP |
1279 | this execution. On a 32 bit system the structure is 32 bytes, |
1280 | on a 64 bit system the structure is 40 bytes (due to the larger | |
1281 | pointer sizes). Objects in the table are not deallocated until | |
882227f1 | 1282 | fast-import terminates. Importing 2 million objects on a 32 bit system |
6e411d20 SP |
1283 | will require approximately 64 MiB of memory. |
1284 | ||
1285 | The object table is actually a hashtable keyed on the object name | |
882227f1 | 1286 | (the unique SHA-1). This storage configuration allows fast-import to reuse |
6e411d20 SP |
1287 | an existing or already written object and avoid writing duplicates |
1288 | to the output packfile. Duplicate blobs are surprisingly common | |
1289 | in an import, typically due to branch merges in the source. | |
1290 | ||
1291 | per mark | |
1292 | ~~~~~~~~ | |
1293 | Marks are stored in a sparse array, using 1 pointer (4 bytes or 8 | |
1294 | bytes, depending on pointer size) per mark. Although the array | |
1295 | is sparse, frontends are still strongly encouraged to use marks | |
1296 | between 1 and n, where n is the total number of marks required for | |
1297 | this import. | |
1298 | ||
1299 | per branch | |
1300 | ~~~~~~~~~~ | |
1301 | Branches are classified as active and inactive. The memory usage | |
1302 | of the two classes is significantly different. | |
1303 | ||
1304 | Inactive branches are stored in a structure which uses 96 or 120 | |
1305 | bytes (32 bit or 64 bit systems, respectively), plus the length of | |
882227f1 | 1306 | the branch name (typically under 200 bytes), per branch. fast-import will |
6e411d20 SP |
1307 | easily handle as many as 10,000 inactive branches in under 2 MiB |
1308 | of memory. | |
1309 | ||
1310 | Active branches have the same overhead as inactive branches, but | |
1311 | also contain copies of every tree that has been recently modified on | |
1312 | that branch. If subtree `include` has not been modified since the | |
1313 | branch became active, its contents will not be loaded into memory, | |
1314 | but if subtree `src` has been modified by a commit since the branch | |
1315 | became active, then its contents will be loaded in memory. | |
1316 | ||
1317 | As active branches store metadata about the files contained on that | |
1318 | branch, their in-memory storage size can grow to a considerable size | |
1319 | (see below). | |
1320 | ||
882227f1 | 1321 | fast-import automatically moves active branches to inactive status based on |
6e411d20 SP |
1322 | a simple least-recently-used algorithm. The LRU chain is updated on |
1323 | each `commit` command. The maximum number of active branches can be | |
c499d768 | 1324 | increased or decreased on the command line with \--active-branches=. |
6e411d20 SP |
1325 | |
1326 | per active tree | |
1327 | ~~~~~~~~~~~~~~~ | |
1328 | Trees (aka directories) use just 12 bytes of memory on top of the | |
1329 | memory required for their entries (see ``per active file'' below). | |
02783075 | 1330 | The cost of a tree is virtually 0, as its overhead amortizes out |
6e411d20 SP |
1331 | over the individual file entries. |
1332 | ||
1333 | per active file entry | |
1334 | ~~~~~~~~~~~~~~~~~~~~~ | |
1335 | Files (and pointers to subtrees) within active trees require 52 or 64 | |
1336 | bytes (32/64 bit platforms) per entry. To conserve space, file and | |
1337 | tree names are pooled in a common string table, allowing the filename | |
1338 | ``Makefile'' to use just 16 bytes (after including the string header | |
1339 | overhead) no matter how many times it occurs within the project. | |
1340 | ||
1341 | The active branch LRU, when coupled with the filename string pool | |
882227f1 | 1342 | and lazy loading of subtrees, allows fast-import to efficiently import |
6e411d20 SP |
1343 | projects with 2,000+ branches and 45,114+ files in a very limited |
1344 | memory footprint (less than 2.7 MiB per active branch). | |
1345 | ||
dc01f59d JN |
1346 | Signals |
1347 | ------- | |
1348 | Sending *SIGUSR1* to the 'git fast-import' process ends the current | |
1349 | packfile early, simulating a `checkpoint` command. The impatient | |
1350 | operator can use this facility to peek at the objects and refs from an | |
1351 | import in progress, at the cost of some added running time and worse | |
1352 | compression. | |
6e411d20 | 1353 | |
6e411d20 SP |
1354 | GIT |
1355 | --- | |
9e1f0a85 | 1356 | Part of the linkgit:git[1] suite |