]>
Commit | Line | Data |
---|---|---|
6e411d20 SP |
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 | -------- | |
b1889c36 | 11 | frontend | 'git fast-import' [options] |
6e411d20 SP |
12 | |
13 | DESCRIPTION | |
14 | ----------- | |
15 | This program is usually not what the end user wants to run directly. | |
16 | Most end users want to use one of the existing frontend programs, | |
17 | which parses a specific type of foreign source and feeds the contents | |
0b444cdb | 18 | stored there to 'git fast-import'. |
6e411d20 | 19 | |
882227f1 | 20 | fast-import reads a mixed command/data stream from standard input and |
6e411d20 SP |
21 | writes one or more packfiles directly into the current repository. |
22 | When EOF is received on standard input, fast import writes out | |
23 | updated branch and tag refs, fully updating the current repository | |
24 | with the newly imported data. | |
25 | ||
882227f1 | 26 | The fast-import backend itself can import into an empty repository (one that |
0b444cdb | 27 | has already been initialized by 'git init') or incrementally |
6e411d20 SP |
28 | update an existing populated repository. Whether or not incremental |
29 | imports are supported from a particular foreign source depends on | |
30 | the frontend program in use. | |
31 | ||
32 | ||
33 | OPTIONS | |
34 | ------- | |
63e0c8b3 SP |
35 | --date-format=<fmt>:: |
36 | Specify the type of dates the frontend will supply to | |
882227f1 | 37 | fast-import within `author`, `committer` and `tagger` commands. |
63e0c8b3 SP |
38 | See ``Date Formats'' below for details about which formats |
39 | are supported, and their syntax. | |
40 | ||
7073e69e SP |
41 | --force:: |
42 | Force updating modified existing branches, even if doing | |
43 | so would cause commits to be lost (as the new commit does | |
44 | not contain the old commit). | |
45 | ||
6e411d20 | 46 | --max-pack-size=<n>:: |
4d0cc224 | 47 | Maximum size of each output packfile. |
89e0a3a1 | 48 | The default is unlimited. |
6e411d20 | 49 | |
5eef828b SP |
50 | --big-file-threshold=<n>:: |
51 | Maximum size of a blob that fast-import will attempt to | |
52 | create a delta for, expressed in bytes. The default is 512m | |
53 | (512 MiB). Some importers may wish to lower this on systems | |
54 | with constrained memory. | |
55 | ||
6e411d20 SP |
56 | --depth=<n>:: |
57 | Maximum delta depth, for blob and tree deltification. | |
58 | Default is 10. | |
59 | ||
60 | --active-branches=<n>:: | |
61 | Maximum number of branches to maintain active at once. | |
62 | See ``Memory Utilization'' below for details. Default is 5. | |
63 | ||
64 | --export-marks=<file>:: | |
65 | Dumps the internal marks table to <file> when complete. | |
66 | Marks are written one per line as `:markid SHA-1`. | |
67 | Frontends can use this file to validate imports after they | |
e8438420 SP |
68 | have been completed, or to save the marks table across |
69 | incremental runs. As <file> is only opened and truncated | |
70 | at checkpoint (or completion) the same path can also be | |
71 | safely given to \--import-marks. | |
72 | ||
73 | --import-marks=<file>:: | |
74 | Before processing any input, load the marks specified in | |
75 | <file>. The input file must exist, must be readable, and | |
76 | must use the same format as produced by \--export-marks. | |
77 | Multiple options may be supplied to import more than one | |
78 | set of marks. If a mark is defined to different values, | |
79 | the last file wins. | |
6e411d20 | 80 | |
bc3c79ae SR |
81 | --relative-marks:: |
82 | After specifying --relative-marks= the paths specified | |
83 | with --import-marks= and --export-marks= are relative | |
84 | to an internal directory in the current repository. | |
85 | In git-fast-import this means that the paths are relative | |
86 | to the .git/info/fast-import directory. However, other | |
87 | importers may use a different location. | |
88 | ||
89 | --no-relative-marks:: | |
90 | Negates a previous --relative-marks. Allows for combining | |
91 | relative and non-relative marks by interweaving | |
92 | --(no-)-relative-marks= with the --(import|export)-marks= | |
93 | options. | |
94 | ||
85c62395 DB |
95 | --cat-blob-fd=<fd>:: |
96 | Specify the file descriptor that will be written to | |
97 | when the `cat-blob` command is encountered in the stream. | |
98 | The default behaviour is to write to `stdout`. | |
99 | ||
bdf1c06d SP |
100 | --export-pack-edges=<file>:: |
101 | After creating a packfile, print a line of data to | |
102 | <file> listing the filename of the packfile and the last | |
103 | commit on each branch that was written to that packfile. | |
104 | This information may be useful after importing projects | |
105 | whose total object set exceeds the 4 GiB packfile limit, | |
106 | as these commits can be used as edge points during calls | |
0b444cdb | 107 | to 'git pack-objects'. |
bdf1c06d | 108 | |
c499d768 | 109 | --quiet:: |
882227f1 | 110 | Disable all non-fatal output, making fast-import silent when it |
7f9d77f2 | 111 | is successful. This option disables the output shown by |
c499d768 SP |
112 | \--stats. |
113 | ||
114 | --stats:: | |
882227f1 | 115 | Display some basic statistics about the objects fast-import has |
c499d768 | 116 | created, the packfiles they were stored into, and the |
882227f1 | 117 | memory used by fast-import during this run. Showing this output |
c499d768 SP |
118 | is currently the default, but can be disabled with \--quiet. |
119 | ||
120 | ||
6e411d20 SP |
121 | Performance |
122 | ----------- | |
882227f1 | 123 | The design of fast-import allows it to import large projects in a minimum |
6e411d20 | 124 | amount of memory usage and processing time. Assuming the frontend |
882227f1 | 125 | is able to keep up with fast-import and feed it a constant stream of data, |
6e411d20 SP |
126 | import times for projects holding 10+ years of history and containing |
127 | 100,000+ individual commits are generally completed in just 1-2 | |
128 | hours on quite modest (~$2,000 USD) hardware. | |
129 | ||
130 | Most bottlenecks appear to be in foreign source data access (the | |
882227f1 | 131 | source just cannot extract revisions fast enough) or disk IO (fast-import |
6e411d20 SP |
132 | writes as fast as the disk will take the data). Imports will run |
133 | faster if the source data is stored on a different drive than the | |
134 | destination Git repository (due to less IO contention). | |
135 | ||
136 | ||
137 | Development Cost | |
138 | ---------------- | |
882227f1 | 139 | A typical frontend for fast-import tends to weigh in at approximately 200 |
6e411d20 SP |
140 | lines of Perl/Python/Ruby code. Most developers have been able to |
141 | create working importers in just a couple of hours, even though it | |
882227f1 | 142 | is their first exposure to fast-import, and sometimes even to Git. This is |
6e411d20 SP |
143 | an ideal situation, given that most conversion tools are throw-away |
144 | (use once, and never look back). | |
145 | ||
146 | ||
147 | Parallel Operation | |
148 | ------------------ | |
0b444cdb | 149 | Like 'git push' or 'git fetch', imports handled by fast-import are safe to |
6e411d20 | 150 | run alongside parallel `git repack -a -d` or `git gc` invocations, |
0b444cdb | 151 | or any other Git operation (including 'git prune', as loose objects |
882227f1 | 152 | are never used by fast-import). |
6e411d20 | 153 | |
882227f1 SP |
154 | fast-import does not lock the branch or tag refs it is actively importing. |
155 | After the import, during its ref update phase, fast-import tests each | |
7073e69e SP |
156 | existing branch ref to verify the update will be a fast-forward |
157 | update (the commit stored in the ref is contained in the new | |
158 | history of the commit to be written). If the update is not a | |
882227f1 SP |
159 | fast-forward update, fast-import will skip updating that ref and instead |
160 | prints a warning message. fast-import will always attempt to update all | |
7073e69e SP |
161 | branch refs, and does not stop on the first failure. |
162 | ||
6a5d0b0a | 163 | Branch updates can be forced with \--force, but it's recommended that |
c499d768 | 164 | this only be used on an otherwise quiet repository. Using \--force |
7073e69e | 165 | is not necessary for an initial import into an empty repository. |
6e411d20 SP |
166 | |
167 | ||
168 | Technical Discussion | |
169 | -------------------- | |
882227f1 | 170 | fast-import tracks a set of branches in memory. Any branch can be created |
6e411d20 SP |
171 | or modified at any point during the import process by sending a |
172 | `commit` command on the input stream. This design allows a frontend | |
173 | program to process an unlimited number of branches simultaneously, | |
174 | generating commits in the order they are available from the source | |
175 | data. It also simplifies the frontend programs considerably. | |
176 | ||
882227f1 | 177 | fast-import does not use or alter the current working directory, or any |
6e411d20 SP |
178 | file within it. (It does however update the current Git repository, |
179 | as referenced by `GIT_DIR`.) Therefore an import frontend may use | |
180 | the working directory for its own purposes, such as extracting file | |
181 | revisions from the foreign source. This ignorance of the working | |
882227f1 | 182 | directory also allows fast-import to run very quickly, as it does not |
6e411d20 SP |
183 | need to perform any costly file update operations when switching |
184 | between branches. | |
185 | ||
186 | Input Format | |
187 | ------------ | |
188 | With the exception of raw file data (which Git does not interpret) | |
882227f1 | 189 | the fast-import input format is text (ASCII) based. This text based |
6e411d20 SP |
190 | format simplifies development and debugging of frontend programs, |
191 | especially when a higher level language such as Perl, Python or | |
192 | Ruby is being used. | |
193 | ||
882227f1 | 194 | fast-import is very strict about its input. Where we say SP below we mean |
6e411d20 SP |
195 | *exactly* one space. Likewise LF means one (and only one) linefeed. |
196 | Supplying additional whitespace characters will cause unexpected | |
197 | results, such as branch names or file names with leading or trailing | |
882227f1 | 198 | spaces in their name, or early termination of fast-import when it encounters |
6e411d20 SP |
199 | unexpected input. |
200 | ||
401d53fa SP |
201 | Stream Comments |
202 | ~~~~~~~~~~~~~~~ | |
203 | To aid in debugging frontends fast-import ignores any line that | |
204 | begins with `#` (ASCII pound/hash) up to and including the line | |
205 | ending `LF`. A comment line may contain any sequence of bytes | |
206 | that does not contain an LF and therefore may be used to include | |
207 | any detailed debugging information that might be specific to the | |
208 | frontend and useful when inspecting a fast-import data stream. | |
209 | ||
63e0c8b3 SP |
210 | Date Formats |
211 | ~~~~~~~~~~~~ | |
212 | The following date formats are supported. A frontend should select | |
213 | the format it will use for this import by passing the format name | |
c499d768 | 214 | in the \--date-format=<fmt> command line option. |
63e0c8b3 SP |
215 | |
216 | `raw`:: | |
9b92c82f | 217 | This is the Git native format and is `<time> SP <offutc>`. |
882227f1 | 218 | It is also fast-import's default format, if \--date-format was |
63e0c8b3 SP |
219 | not specified. |
220 | + | |
221 | The time of the event is specified by `<time>` as the number of | |
222 | seconds since the UNIX epoch (midnight, Jan 1, 1970, UTC) and is | |
223 | written as an ASCII decimal integer. | |
224 | + | |
9b92c82f SP |
225 | The local offset is specified by `<offutc>` as a positive or negative |
226 | offset from UTC. For example EST (which is 5 hours behind UTC) | |
227 | would be expressed in `<tz>` by ``-0500'' while UTC is ``+0000''. | |
228 | The local offset does not affect `<time>`; it is used only as an | |
229 | advisement to help formatting routines display the timestamp. | |
63e0c8b3 | 230 | + |
9b92c82f SP |
231 | If the local offset is not available in the source material, use |
232 | ``+0000'', or the most common local offset. For example many | |
63e0c8b3 SP |
233 | organizations have a CVS repository which has only ever been accessed |
234 | by users who are located in the same location and timezone. In this | |
f842fdb0 | 235 | case a reasonable offset from UTC could be assumed. |
63e0c8b3 SP |
236 | + |
237 | Unlike the `rfc2822` format, this format is very strict. Any | |
882227f1 | 238 | variation in formatting will cause fast-import to reject the value. |
63e0c8b3 SP |
239 | |
240 | `rfc2822`:: | |
241 | This is the standard email format as described by RFC 2822. | |
242 | + | |
243 | An example value is ``Tue Feb 6 11:22:18 2007 -0500''. The Git | |
f842fdb0 | 244 | parser is accurate, but a little on the lenient side. It is the |
0b444cdb | 245 | same parser used by 'git am' when applying patches |
63e0c8b3 SP |
246 | received from email. |
247 | + | |
248 | Some malformed strings may be accepted as valid dates. In some of | |
249 | these cases Git will still be able to obtain the correct date from | |
250 | the malformed string. There are also some types of malformed | |
251 | strings which Git will parse wrong, and yet consider valid. | |
252 | Seriously malformed strings will be rejected. | |
253 | + | |
9b92c82f SP |
254 | Unlike the `raw` format above, the timezone/UTC offset information |
255 | contained in an RFC 2822 date string is used to adjust the date | |
256 | value to UTC prior to storage. Therefore it is important that | |
257 | this information be as accurate as possible. | |
258 | + | |
f842fdb0 | 259 | If the source material uses RFC 2822 style dates, |
882227f1 | 260 | the frontend should let fast-import handle the parsing and conversion |
63e0c8b3 SP |
261 | (rather than attempting to do it itself) as the Git parser has |
262 | been well tested in the wild. | |
263 | + | |
264 | Frontends should prefer the `raw` format if the source material | |
f842fdb0 | 265 | already uses UNIX-epoch format, can be coaxed to give dates in that |
02783075 | 266 | format, or its format is easily convertible to it, as there is no |
f842fdb0 | 267 | ambiguity in parsing. |
63e0c8b3 SP |
268 | |
269 | `now`:: | |
270 | Always use the current time and timezone. The literal | |
271 | `now` must always be supplied for `<when>`. | |
272 | + | |
273 | This is a toy format. The current time and timezone of this system | |
274 | is always copied into the identity string at the time it is being | |
882227f1 | 275 | created by fast-import. There is no way to specify a different time or |
63e0c8b3 SP |
276 | timezone. |
277 | + | |
6a5d0b0a | 278 | This particular format is supplied as it's short to implement and |
63e0c8b3 SP |
279 | may be useful to a process that wants to create a new commit |
280 | right now, without needing to use a working directory or | |
0b444cdb | 281 | 'git update-index'. |
63e0c8b3 SP |
282 | + |
283 | If separate `author` and `committer` commands are used in a `commit` | |
284 | the timestamps may not match, as the system clock will be polled | |
285 | twice (once for each command). The only way to ensure that both | |
286 | author and committer identity information has the same timestamp | |
287 | is to omit `author` (thus copying from `committer`) or to use a | |
288 | date format other than `now`. | |
289 | ||
6e411d20 SP |
290 | Commands |
291 | ~~~~~~~~ | |
882227f1 | 292 | fast-import accepts several commands to update the current repository |
6e411d20 SP |
293 | and control the current import process. More detailed discussion |
294 | (with examples) of each command follows later. | |
295 | ||
296 | `commit`:: | |
297 | Creates a new branch or updates an existing branch by | |
298 | creating a new commit and updating the branch to point at | |
299 | the newly created commit. | |
300 | ||
301 | `tag`:: | |
302 | Creates an annotated tag object from an existing commit or | |
303 | branch. Lightweight tags are not supported by this command, | |
304 | as they are not recommended for recording meaningful points | |
305 | in time. | |
306 | ||
307 | `reset`:: | |
308 | Reset an existing branch (or a new branch) to a specific | |
309 | revision. This command must be used to change a branch to | |
310 | a specific revision without making a commit on it. | |
311 | ||
312 | `blob`:: | |
313 | Convert raw file data into a blob, for future use in a | |
314 | `commit` command. This command is optional and is not | |
315 | needed to perform an import. | |
316 | ||
317 | `checkpoint`:: | |
882227f1 | 318 | Forces fast-import to close the current packfile, generate its |
6e411d20 SP |
319 | unique SHA-1 checksum and index, and start a new packfile. |
320 | This command is optional and is not needed to perform | |
321 | an import. | |
322 | ||
ac053c02 SP |
323 | `progress`:: |
324 | Causes fast-import to echo the entire line to its own | |
325 | standard output. This command is optional and is not needed | |
326 | to perform an import. | |
327 | ||
85c62395 DB |
328 | `cat-blob`:: |
329 | Causes fast-import to print a blob in 'cat-file --batch' | |
330 | format to the file descriptor set with `--cat-blob-fd` or | |
331 | `stdout` if unspecified. | |
332 | ||
f963bd5d SR |
333 | `feature`:: |
334 | Require that fast-import supports the specified feature, or | |
335 | abort if it does not. | |
336 | ||
9c8398f0 SR |
337 | `option`:: |
338 | Specify any of the options listed under OPTIONS that do not | |
339 | change stream semantic to suit the frontend's needs. This | |
340 | command is optional and is not needed to perform an import. | |
341 | ||
6e411d20 SP |
342 | `commit` |
343 | ~~~~~~~~ | |
344 | Create or update a branch with a new commit, recording one logical | |
345 | change to the project. | |
346 | ||
347 | .... | |
348 | 'commit' SP <ref> LF | |
349 | mark? | |
74fbd118 SP |
350 | ('author' (SP <name>)? SP LT <email> GT SP <when> LF)? |
351 | 'committer' (SP <name>)? SP LT <email> GT SP <when> LF | |
6e411d20 SP |
352 | data |
353 | ('from' SP <committish> LF)? | |
354 | ('merge' SP <committish> LF)? | |
a8dd2e7d | 355 | (filemodify | filedelete | filecopy | filerename | filedeleteall | notemodify)* |
1fdb649c | 356 | LF? |
6e411d20 SP |
357 | .... |
358 | ||
359 | where `<ref>` is the name of the branch to make the commit on. | |
360 | Typically branch names are prefixed with `refs/heads/` in | |
361 | Git, so importing the CVS branch symbol `RELENG-1_0` would use | |
362 | `refs/heads/RELENG-1_0` for the value of `<ref>`. The value of | |
363 | `<ref>` must be a valid refname in Git. As `LF` is not valid in | |
364 | a Git refname, no quoting or escaping syntax is supported here. | |
365 | ||
882227f1 | 366 | A `mark` command may optionally appear, requesting fast-import to save a |
6e411d20 SP |
367 | reference to the newly created commit for future use by the frontend |
368 | (see below for format). It is very common for frontends to mark | |
369 | every commit they create, thereby allowing future branch creation | |
370 | from any imported commit. | |
371 | ||
372 | The `data` command following `committer` must supply the commit | |
373 | message (see below for `data` command syntax). To import an empty | |
374 | commit message use a 0 length data. Commit messages are free-form | |
375 | and are not interpreted by Git. Currently they must be encoded in | |
882227f1 | 376 | UTF-8, as fast-import does not permit other encodings to be specified. |
6e411d20 | 377 | |
a8dd2e7d JH |
378 | Zero or more `filemodify`, `filedelete`, `filecopy`, `filerename`, |
379 | `filedeleteall` and `notemodify` commands | |
825769a8 SP |
380 | may be included to update the contents of the branch prior to |
381 | creating the commit. These commands may be supplied in any order. | |
02783075 | 382 | However it is recommended that a `filedeleteall` command precede |
a8dd2e7d JH |
383 | all `filemodify`, `filecopy`, `filerename` and `notemodify` commands in |
384 | the same commit, as `filedeleteall` wipes the branch clean (see below). | |
6e411d20 | 385 | |
1fdb649c SP |
386 | The `LF` after the command is optional (it used to be required). |
387 | ||
6e411d20 SP |
388 | `author` |
389 | ^^^^^^^^ | |
390 | An `author` command may optionally appear, if the author information | |
391 | might differ from the committer information. If `author` is omitted | |
882227f1 | 392 | then fast-import will automatically use the committer's information for |
6e411d20 SP |
393 | the author portion of the commit. See below for a description of |
394 | the fields in `author`, as they are identical to `committer`. | |
395 | ||
396 | `committer` | |
397 | ^^^^^^^^^^^ | |
398 | The `committer` command indicates who made this commit, and when | |
399 | they made it. | |
400 | ||
401 | Here `<name>` is the person's display name (for example | |
402 | ``Com M Itter'') and `<email>` is the person's email address | |
403 | (``cm@example.com''). `LT` and `GT` are the literal less-than (\x3c) | |
404 | and greater-than (\x3e) symbols. These are required to delimit | |
405 | the email address from the other fields in the line. Note that | |
406 | `<name>` is free-form and may contain any sequence of bytes, except | |
407 | `LT` and `LF`. It is typically UTF-8 encoded. | |
408 | ||
63e0c8b3 | 409 | The time of the change is specified by `<when>` using the date format |
c499d768 | 410 | that was selected by the \--date-format=<fmt> command line option. |
63e0c8b3 SP |
411 | See ``Date Formats'' above for the set of supported formats, and |
412 | their syntax. | |
6e411d20 SP |
413 | |
414 | `from` | |
415 | ^^^^^^ | |
ea5e370a SP |
416 | The `from` command is used to specify the commit to initialize |
417 | this branch from. This revision will be the first ancestor of the | |
418 | new commit. | |
419 | ||
420 | Omitting the `from` command in the first commit of a new branch | |
421 | will cause fast-import to create that commit with no ancestor. This | |
422 | tends to be desired only for the initial commit of a project. | |
9b33fa08 EB |
423 | If the frontend creates all files from scratch when making a new |
424 | branch, a `merge` command may be used instead of `from` to start | |
425 | the commit with an empty tree. | |
ea5e370a SP |
426 | Omitting the `from` command on existing branches is usually desired, |
427 | as the current commit on that branch is automatically assumed to | |
428 | be the first ancestor of the new commit. | |
6e411d20 SP |
429 | |
430 | As `LF` is not valid in a Git refname or SHA-1 expression, no | |
431 | quoting or escaping syntax is supported within `<committish>`. | |
432 | ||
433 | Here `<committish>` is any of the following: | |
434 | ||
882227f1 | 435 | * The name of an existing branch already in fast-import's internal branch |
6a5d0b0a | 436 | table. If fast-import doesn't know the name, it's treated as a SHA-1 |
6e411d20 SP |
437 | expression. |
438 | ||
439 | * A mark reference, `:<idnum>`, where `<idnum>` is the mark number. | |
440 | + | |
882227f1 | 441 | The reason fast-import uses `:` to denote a mark reference is this character |
6e411d20 | 442 | is not legal in a Git branch name. The leading `:` makes it easy |
02783075 | 443 | to distinguish between the mark 42 (`:42`) and the branch 42 (`42` |
6e411d20 SP |
444 | or `refs/heads/42`), or an abbreviated SHA-1 which happened to |
445 | consist only of base-10 digits. | |
446 | + | |
447 | Marks must be declared (via `mark`) before they can be used. | |
448 | ||
449 | * A complete 40 byte or abbreviated commit SHA-1 in hex. | |
450 | ||
451 | * Any valid Git SHA-1 expression that resolves to a commit. See | |
9d83e382 | 452 | ``SPECIFYING REVISIONS'' in linkgit:gitrevisions[7] for details. |
6e411d20 SP |
453 | |
454 | The special case of restarting an incremental import from the | |
455 | current branch value should be written as: | |
456 | ---- | |
457 | from refs/heads/branch^0 | |
458 | ---- | |
882227f1 | 459 | The `{caret}0` suffix is necessary as fast-import does not permit a branch to |
6e411d20 | 460 | start from itself, and the branch is created in memory before the |
209f1298 | 461 | `from` command is even read from the input. Adding `{caret}0` will force |
882227f1 | 462 | fast-import to resolve the commit through Git's revision parsing library, |
6e411d20 SP |
463 | rather than its internal branch table, thereby loading in the |
464 | existing value of the branch. | |
465 | ||
466 | `merge` | |
467 | ^^^^^^^ | |
9b33fa08 EB |
468 | Includes one additional ancestor commit. If the `from` command is |
469 | omitted when creating a new branch, the first `merge` commit will be | |
470 | the first ancestor of the current commit, and the branch will start | |
471 | out with no files. An unlimited number of `merge` commands per | |
882227f1 | 472 | commit are permitted by fast-import, thereby establishing an n-way merge. |
6e411d20 SP |
473 | However Git's other tools never create commits with more than 15 |
474 | additional ancestors (forming a 16-way merge). For this reason | |
475 | it is suggested that frontends do not use more than 15 `merge` | |
9b33fa08 | 476 | commands per commit; 16, if starting a new, empty branch. |
6e411d20 SP |
477 | |
478 | Here `<committish>` is any of the commit specification expressions | |
479 | also accepted by `from` (see above). | |
480 | ||
481 | `filemodify` | |
ef94edb5 | 482 | ^^^^^^^^^^^^ |
6e411d20 SP |
483 | Included in a `commit` command to add a new file or change the |
484 | content of an existing file. This command has two different means | |
485 | of specifying the content of the file. | |
486 | ||
487 | External data format:: | |
488 | The data content for the file was already supplied by a prior | |
489 | `blob` command. The frontend just needs to connect it. | |
490 | + | |
491 | .... | |
492 | 'M' SP <mode> SP <dataref> SP <path> LF | |
493 | .... | |
494 | + | |
334fba65 | 495 | Here usually `<dataref>` must be either a mark reference (`:<idnum>`) |
6e411d20 | 496 | set by a prior `blob` command, or a full 40-byte SHA-1 of an |
334fba65 JN |
497 | existing Git blob object. If `<mode>` is `040000`` then |
498 | `<dataref>` must be the full 40-byte SHA-1 of an existing | |
499 | Git tree object or a mark reference set with `--import-marks`. | |
6e411d20 SP |
500 | |
501 | Inline data format:: | |
502 | The data content for the file has not been supplied yet. | |
503 | The frontend wants to supply it as part of this modify | |
504 | command. | |
505 | + | |
506 | .... | |
507 | 'M' SP <mode> SP 'inline' SP <path> LF | |
508 | data | |
509 | .... | |
510 | + | |
511 | See below for a detailed description of the `data` command. | |
512 | ||
513 | In both formats `<mode>` is the type of file entry, specified | |
514 | in octal. Git only supports the following modes: | |
515 | ||
516 | * `100644` or `644`: A normal (not-executable) file. The majority | |
517 | of files in most projects use this mode. If in doubt, this is | |
518 | what you want. | |
519 | * `100755` or `755`: A normal, but executable, file. | |
9981b6d9 | 520 | * `120000`: A symlink, the content of the file will be the link target. |
03db4525 AG |
521 | * `160000`: A gitlink, SHA-1 of the object refers to a commit in |
522 | another repository. Git links can only be specified by SHA or through | |
523 | a commit mark. They are used to implement submodules. | |
334fba65 JN |
524 | * `040000`: A subdirectory. Subdirectories can only be specified by |
525 | SHA or through a tree mark set with `--import-marks`. | |
6e411d20 SP |
526 | |
527 | In both formats `<path>` is the complete path of the file to be added | |
528 | (if not already existing) or modified (if already existing). | |
529 | ||
c4431d38 | 530 | A `<path>` string must use UNIX-style directory separators (forward |
6e411d20 SP |
531 | slash `/`), may contain any byte other than `LF`, and must not |
532 | start with double quote (`"`). | |
533 | ||
534 | If an `LF` or double quote must be encoded into `<path>` shell-style | |
535 | quoting should be used, e.g. `"path/with\n and \" in it"`. | |
536 | ||
2794ad52 DB |
537 | Additionally, in `040000` mode, `<path>` may also be an empty string |
538 | (`""`) to specify the root of the tree. | |
539 | ||
02783075 | 540 | The value of `<path>` must be in canonical form. That is it must not: |
6e411d20 SP |
541 | |
542 | * contain an empty directory component (e.g. `foo//bar` is invalid), | |
c4431d38 JK |
543 | * end with a directory separator (e.g. `foo/` is invalid), |
544 | * start with a directory separator (e.g. `/foo` is invalid), | |
6e411d20 SP |
545 | * contain the special component `.` or `..` (e.g. `foo/./bar` and |
546 | `foo/../bar` are invalid). | |
547 | ||
548 | It is recommended that `<path>` always be encoded using UTF-8. | |
549 | ||
6e411d20 | 550 | `filedelete` |
ef94edb5 | 551 | ^^^^^^^^^^^^ |
512e44b2 SP |
552 | Included in a `commit` command to remove a file or recursively |
553 | delete an entire directory from the branch. If the file or directory | |
554 | removal makes its parent directory empty, the parent directory will | |
6e411d20 SP |
555 | be automatically removed too. This cascades up the tree until the |
556 | first non-empty directory or the root is reached. | |
557 | ||
558 | .... | |
559 | 'D' SP <path> LF | |
560 | .... | |
561 | ||
512e44b2 SP |
562 | here `<path>` is the complete path of the file or subdirectory to |
563 | be removed from the branch. | |
6e411d20 SP |
564 | See `filemodify` above for a detailed description of `<path>`. |
565 | ||
b6f3481b SP |
566 | `filecopy` |
567 | ^^^^^^^^^^^^ | |
568 | Recursively copies an existing file or subdirectory to a different | |
569 | location within the branch. The existing file or directory must | |
570 | exist. If the destination exists it will be completely replaced | |
571 | by the content copied from the source. | |
572 | ||
573 | .... | |
574 | 'C' SP <path> SP <path> LF | |
575 | .... | |
576 | ||
577 | here the first `<path>` is the source location and the second | |
578 | `<path>` is the destination. See `filemodify` above for a detailed | |
579 | description of what `<path>` may look like. To use a source path | |
580 | that contains SP the path must be quoted. | |
581 | ||
582 | A `filecopy` command takes effect immediately. Once the source | |
583 | location has been copied to the destination any future commands | |
584 | applied to the source location will not impact the destination of | |
585 | the copy. | |
586 | ||
f39a946a SP |
587 | `filerename` |
588 | ^^^^^^^^^^^^ | |
589 | Renames an existing file or subdirectory to a different location | |
590 | within the branch. The existing file or directory must exist. If | |
591 | the destination exists it will be replaced by the source directory. | |
592 | ||
593 | .... | |
594 | 'R' SP <path> SP <path> LF | |
595 | .... | |
596 | ||
597 | here the first `<path>` is the source location and the second | |
598 | `<path>` is the destination. See `filemodify` above for a detailed | |
599 | description of what `<path>` may look like. To use a source path | |
600 | that contains SP the path must be quoted. | |
601 | ||
602 | A `filerename` command takes effect immediately. Once the source | |
603 | location has been renamed to the destination any future commands | |
604 | applied to the source location will create new files there and not | |
605 | impact the destination of the rename. | |
606 | ||
b6f3481b SP |
607 | Note that a `filerename` is the same as a `filecopy` followed by a |
608 | `filedelete` of the source location. There is a slight performance | |
609 | advantage to using `filerename`, but the advantage is so small | |
610 | that it is never worth trying to convert a delete/add pair in | |
611 | source material into a rename for fast-import. This `filerename` | |
612 | command is provided just to simplify frontends that already have | |
613 | rename information and don't want bother with decomposing it into a | |
614 | `filecopy` followed by a `filedelete`. | |
615 | ||
825769a8 SP |
616 | `filedeleteall` |
617 | ^^^^^^^^^^^^^^^ | |
618 | Included in a `commit` command to remove all files (and also all | |
619 | directories) from the branch. This command resets the internal | |
620 | branch structure to have no files in it, allowing the frontend | |
621 | to subsequently add all interesting files from scratch. | |
622 | ||
623 | .... | |
624 | 'deleteall' LF | |
625 | .... | |
626 | ||
627 | This command is extremely useful if the frontend does not know | |
628 | (or does not care to know) what files are currently on the branch, | |
629 | and therefore cannot generate the proper `filedelete` commands to | |
630 | update the content. | |
631 | ||
632 | Issuing a `filedeleteall` followed by the needed `filemodify` | |
633 | commands to set the correct content will produce the same results | |
634 | as sending only the needed `filemodify` and `filedelete` commands. | |
882227f1 | 635 | The `filedeleteall` approach may however require fast-import to use slightly |
825769a8 SP |
636 | more memory per active branch (less than 1 MiB for even most large |
637 | projects); so frontends that can easily obtain only the affected | |
638 | paths for a commit are encouraged to do so. | |
639 | ||
a8dd2e7d JH |
640 | `notemodify` |
641 | ^^^^^^^^^^^^ | |
642 | Included in a `commit` command to add a new note (annotating a given | |
643 | commit) or change the content of an existing note. This command has | |
644 | two different means of specifying the content of the note. | |
645 | ||
646 | External data format:: | |
647 | The data content for the note was already supplied by a prior | |
648 | `blob` command. The frontend just needs to connect it to the | |
649 | commit that is to be annotated. | |
650 | + | |
651 | .... | |
652 | 'N' SP <dataref> SP <committish> LF | |
653 | .... | |
654 | + | |
655 | Here `<dataref>` can be either a mark reference (`:<idnum>`) | |
656 | set by a prior `blob` command, or a full 40-byte SHA-1 of an | |
657 | existing Git blob object. | |
658 | ||
659 | Inline data format:: | |
660 | The data content for the note has not been supplied yet. | |
661 | The frontend wants to supply it as part of this modify | |
662 | command. | |
663 | + | |
664 | .... | |
665 | 'N' SP 'inline' SP <committish> LF | |
666 | data | |
667 | .... | |
668 | + | |
669 | See below for a detailed description of the `data` command. | |
670 | ||
671 | In both formats `<committish>` is any of the commit specification | |
672 | expressions also accepted by `from` (see above). | |
673 | ||
6e411d20 SP |
674 | `mark` |
675 | ~~~~~~ | |
882227f1 | 676 | Arranges for fast-import to save a reference to the current object, allowing |
6e411d20 SP |
677 | the frontend to recall this object at a future point in time, without |
678 | knowing its SHA-1. Here the current object is the object creation | |
679 | command the `mark` command appears within. This can be `commit`, | |
680 | `tag`, and `blob`, but `commit` is the most common usage. | |
681 | ||
682 | .... | |
683 | 'mark' SP ':' <idnum> LF | |
684 | .... | |
685 | ||
686 | where `<idnum>` is the number assigned by the frontend to this mark. | |
ef94edb5 SP |
687 | The value of `<idnum>` is expressed as an ASCII decimal integer. |
688 | The value 0 is reserved and cannot be used as | |
6e411d20 SP |
689 | a mark. Only values greater than or equal to 1 may be used as marks. |
690 | ||
691 | New marks are created automatically. Existing marks can be moved | |
692 | to another object simply by reusing the same `<idnum>` in another | |
693 | `mark` command. | |
694 | ||
695 | `tag` | |
696 | ~~~~~ | |
697 | Creates an annotated tag referring to a specific commit. To create | |
698 | lightweight (non-annotated) tags see the `reset` command below. | |
699 | ||
700 | .... | |
701 | 'tag' SP <name> LF | |
702 | 'from' SP <committish> LF | |
74fbd118 | 703 | 'tagger' (SP <name>)? SP LT <email> GT SP <when> LF |
6e411d20 | 704 | data |
6e411d20 SP |
705 | .... |
706 | ||
707 | where `<name>` is the name of the tag to create. | |
708 | ||
709 | Tag names are automatically prefixed with `refs/tags/` when stored | |
710 | in Git, so importing the CVS branch symbol `RELENG-1_0-FINAL` would | |
882227f1 | 711 | use just `RELENG-1_0-FINAL` for `<name>`, and fast-import will write the |
6e411d20 SP |
712 | corresponding ref as `refs/tags/RELENG-1_0-FINAL`. |
713 | ||
714 | The value of `<name>` must be a valid refname in Git and therefore | |
715 | may contain forward slashes. As `LF` is not valid in a Git refname, | |
716 | no quoting or escaping syntax is supported here. | |
717 | ||
718 | The `from` command is the same as in the `commit` command; see | |
719 | above for details. | |
720 | ||
721 | The `tagger` command uses the same format as `committer` within | |
722 | `commit`; again see above for details. | |
723 | ||
724 | The `data` command following `tagger` must supply the annotated tag | |
725 | message (see below for `data` command syntax). To import an empty | |
726 | tag message use a 0 length data. Tag messages are free-form and are | |
727 | not interpreted by Git. Currently they must be encoded in UTF-8, | |
882227f1 | 728 | as fast-import does not permit other encodings to be specified. |
6e411d20 | 729 | |
882227f1 | 730 | Signing annotated tags during import from within fast-import is not |
6e411d20 SP |
731 | supported. Trying to include your own PGP/GPG signature is not |
732 | recommended, as the frontend does not (easily) have access to the | |
733 | complete set of bytes which normally goes into such a signature. | |
882227f1 | 734 | If signing is required, create lightweight tags from within fast-import with |
6e411d20 | 735 | `reset`, then create the annotated versions of those tags offline |
0b444cdb | 736 | with the standard 'git tag' process. |
6e411d20 SP |
737 | |
738 | `reset` | |
739 | ~~~~~~~ | |
740 | Creates (or recreates) the named branch, optionally starting from | |
741 | a specific revision. The reset command allows a frontend to issue | |
742 | a new `from` command for an existing branch, or to create a new | |
743 | branch from an existing commit without creating a new commit. | |
744 | ||
745 | .... | |
746 | 'reset' SP <ref> LF | |
747 | ('from' SP <committish> LF)? | |
1fdb649c | 748 | LF? |
6e411d20 SP |
749 | .... |
750 | ||
751 | For a detailed description of `<ref>` and `<committish>` see above | |
752 | under `commit` and `from`. | |
753 | ||
1fdb649c SP |
754 | The `LF` after the command is optional (it used to be required). |
755 | ||
6e411d20 SP |
756 | The `reset` command can also be used to create lightweight |
757 | (non-annotated) tags. For example: | |
758 | ||
759 | ==== | |
760 | reset refs/tags/938 | |
761 | from :938 | |
762 | ==== | |
763 | ||
764 | would create the lightweight tag `refs/tags/938` referring to | |
765 | whatever commit mark `:938` references. | |
766 | ||
767 | `blob` | |
768 | ~~~~~~ | |
769 | Requests writing one file revision to the packfile. The revision | |
770 | is not connected to any commit; this connection must be formed in | |
771 | a subsequent `commit` command by referencing the blob through an | |
772 | assigned mark. | |
773 | ||
774 | .... | |
775 | 'blob' LF | |
776 | mark? | |
777 | data | |
778 | .... | |
779 | ||
780 | The mark command is optional here as some frontends have chosen | |
781 | to generate the Git SHA-1 for the blob on their own, and feed that | |
6a5d0b0a | 782 | directly to `commit`. This is typically more work than it's worth |
6e411d20 SP |
783 | however, as marks are inexpensive to store and easy to use. |
784 | ||
785 | `data` | |
786 | ~~~~~~ | |
787 | Supplies raw data (for use as blob/file content, commit messages, or | |
882227f1 | 788 | annotated tag messages) to fast-import. Data can be supplied using an exact |
6e411d20 SP |
789 | byte count or delimited with a terminating line. Real frontends |
790 | intended for production-quality conversions should always use the | |
791 | exact byte count format, as it is more robust and performs better. | |
882227f1 | 792 | The delimited format is intended primarily for testing fast-import. |
6e411d20 | 793 | |
401d53fa SP |
794 | Comment lines appearing within the `<raw>` part of `data` commands |
795 | are always taken to be part of the body of the data and are therefore | |
796 | never ignored by fast-import. This makes it safe to import any | |
797 | file/message content whose lines might start with `#`. | |
798 | ||
ef94edb5 SP |
799 | Exact byte count format:: |
800 | The frontend must specify the number of bytes of data. | |
801 | + | |
6e411d20 SP |
802 | .... |
803 | 'data' SP <count> LF | |
2c570cde | 804 | <raw> LF? |
6e411d20 | 805 | .... |
ef94edb5 | 806 | + |
6e411d20 | 807 | where `<count>` is the exact number of bytes appearing within |
ef94edb5 SP |
808 | `<raw>`. The value of `<count>` is expressed as an ASCII decimal |
809 | integer. The `LF` on either side of `<raw>` is not | |
6e411d20 | 810 | included in `<count>` and will not be included in the imported data. |
2c570cde SP |
811 | + |
812 | The `LF` after `<raw>` is optional (it used to be required) but | |
813 | recommended. Always including it makes debugging a fast-import | |
814 | stream easier as the next command always starts in column 0 | |
815 | of the next line, even if `<raw>` did not end with an `LF`. | |
6e411d20 | 816 | |
ef94edb5 SP |
817 | Delimited format:: |
818 | A delimiter string is used to mark the end of the data. | |
882227f1 | 819 | fast-import will compute the length by searching for the delimiter. |
02783075 | 820 | This format is primarily useful for testing and is not |
ef94edb5 SP |
821 | recommended for real data. |
822 | + | |
6e411d20 SP |
823 | .... |
824 | 'data' SP '<<' <delim> LF | |
825 | <raw> LF | |
826 | <delim> LF | |
2c570cde | 827 | LF? |
6e411d20 | 828 | .... |
ef94edb5 | 829 | + |
6e411d20 SP |
830 | where `<delim>` is the chosen delimiter string. The string `<delim>` |
831 | must not appear on a line by itself within `<raw>`, as otherwise | |
882227f1 | 832 | fast-import will think the data ends earlier than it really does. The `LF` |
6e411d20 SP |
833 | immediately trailing `<raw>` is part of `<raw>`. This is one of |
834 | the limitations of the delimited format, it is impossible to supply | |
835 | a data chunk which does not have an LF as its last byte. | |
2c570cde SP |
836 | + |
837 | The `LF` after `<delim> LF` is optional (it used to be required). | |
6e411d20 SP |
838 | |
839 | `checkpoint` | |
840 | ~~~~~~~~~~~~ | |
882227f1 | 841 | Forces fast-import to close the current packfile, start a new one, and to |
820b9310 | 842 | save out all current branch refs, tags and marks. |
6e411d20 SP |
843 | |
844 | .... | |
845 | 'checkpoint' LF | |
1fdb649c | 846 | LF? |
6e411d20 SP |
847 | .... |
848 | ||
882227f1 | 849 | Note that fast-import automatically switches packfiles when the current |
820b9310 | 850 | packfile reaches \--max-pack-size, or 4 GiB, whichever limit is |
882227f1 | 851 | smaller. During an automatic packfile switch fast-import does not update |
820b9310 SP |
852 | the branch refs, tags or marks. |
853 | ||
854 | As a `checkpoint` can require a significant amount of CPU time and | |
855 | disk IO (to compute the overall pack SHA-1 checksum, generate the | |
856 | corresponding index file, and update the refs) it can easily take | |
857 | several minutes for a single `checkpoint` command to complete. | |
858 | ||
859 | Frontends may choose to issue checkpoints during extremely large | |
860 | and long running imports, or when they need to allow another Git | |
861 | process access to a branch. However given that a 30 GiB Subversion | |
882227f1 | 862 | repository can be loaded into Git through fast-import in about 3 hours, |
820b9310 SP |
863 | explicit checkpointing may not be necessary. |
864 | ||
1fdb649c | 865 | The `LF` after the command is optional (it used to be required). |
820b9310 | 866 | |
ac053c02 SP |
867 | `progress` |
868 | ~~~~~~~~~~ | |
869 | Causes fast-import to print the entire `progress` line unmodified to | |
870 | its standard output channel (file descriptor 1) when the command is | |
871 | processed from the input stream. The command otherwise has no impact | |
872 | on the current import, or on any of fast-import's internal state. | |
873 | ||
874 | .... | |
875 | 'progress' SP <any> LF | |
876 | LF? | |
877 | .... | |
878 | ||
879 | The `<any>` part of the command may contain any sequence of bytes | |
880 | that does not contain `LF`. The `LF` after the command is optional. | |
881 | Callers may wish to process the output through a tool such as sed to | |
882 | remove the leading part of the line, for example: | |
883 | ||
884 | ==== | |
b1889c36 | 885 | frontend | git fast-import | sed 's/^progress //' |
ac053c02 SP |
886 | ==== |
887 | ||
888 | Placing a `progress` command immediately after a `checkpoint` will | |
889 | inform the reader when the `checkpoint` has been completed and it | |
890 | can safely access the refs that fast-import updated. | |
891 | ||
85c62395 DB |
892 | `cat-blob` |
893 | ~~~~~~~~~~ | |
894 | Causes fast-import to print a blob to a file descriptor previously | |
895 | arranged with the `--cat-blob-fd` argument. The command otherwise | |
896 | has no impact on the current import; its main purpose is to | |
897 | retrieve blobs that may be in fast-import's memory but not | |
898 | accessible from the target repository. | |
899 | ||
900 | .... | |
901 | 'cat-blob' SP <dataref> LF | |
902 | .... | |
903 | ||
904 | The `<dataref>` can be either a mark reference (`:<idnum>`) | |
905 | set previously or a full 40-byte SHA-1 of a Git blob, preexisting or | |
906 | ready to be written. | |
907 | ||
908 | output uses the same format as `git cat-file --batch`: | |
909 | ||
910 | ==== | |
911 | <sha1> SP 'blob' SP <size> LF | |
912 | <contents> LF | |
913 | ==== | |
914 | ||
777f80d7 JN |
915 | This command can be used anywhere in the stream that comments are |
916 | accepted. In particular, the `cat-blob` command can be used in the | |
917 | middle of a commit but not in the middle of a `data` command. | |
918 | ||
f963bd5d SR |
919 | `feature` |
920 | ~~~~~~~~~ | |
921 | Require that fast-import supports the specified feature, or abort if | |
922 | it does not. | |
923 | ||
924 | .... | |
4980fffb | 925 | 'feature' SP <feature> ('=' <argument>)? LF |
f963bd5d SR |
926 | .... |
927 | ||
4980fffb | 928 | The <feature> part of the command may be any one of the following: |
f963bd5d | 929 | |
4980fffb JN |
930 | date-format:: |
931 | export-marks:: | |
932 | relative-marks:: | |
933 | no-relative-marks:: | |
934 | force:: | |
935 | Act as though the corresponding command-line option with | |
936 | a leading '--' was passed on the command line | |
937 | (see OPTIONS, above). | |
f963bd5d | 938 | |
4980fffb JN |
939 | import-marks:: |
940 | Like --import-marks except in two respects: first, only one | |
941 | "feature import-marks" command is allowed per stream; | |
942 | second, an --import-marks= command-line option overrides | |
943 | any "feature import-marks" command in the stream. | |
f963bd5d | 944 | |
85c62395 DB |
945 | cat-blob:: |
946 | Ignored. Versions of fast-import not supporting the | |
947 | "cat-blob" command will exit with a message indicating so. | |
948 | This lets the import error out early with a clear message, | |
949 | rather than wasting time on the early part of an import | |
950 | before the unsupported command is detected. | |
081751c8 | 951 | |
9c8398f0 SR |
952 | `option` |
953 | ~~~~~~~~ | |
954 | Processes the specified option so that git fast-import behaves in a | |
955 | way that suits the frontend's needs. | |
956 | Note that options specified by the frontend are overridden by any | |
957 | options the user may specify to git fast-import itself. | |
958 | ||
959 | .... | |
960 | 'option' SP <option> LF | |
961 | .... | |
962 | ||
963 | The `<option>` part of the command may contain any of the options | |
964 | listed in the OPTIONS section that do not change import semantics, | |
965 | without the leading '--' and is treated in the same way. | |
966 | ||
967 | Option commands must be the first commands on the input (not counting | |
968 | feature commands), to give an option command after any non-option | |
969 | command is an error. | |
970 | ||
971 | The following commandline options change import semantics and may therefore | |
972 | not be passed as option: | |
973 | ||
974 | * date-format | |
975 | * import-marks | |
976 | * export-marks | |
85c62395 | 977 | * cat-blob-fd |
9c8398f0 SR |
978 | * force |
979 | ||
e7e5170f SP |
980 | Crash Reports |
981 | ------------- | |
982 | If fast-import is supplied invalid input it will terminate with a | |
983 | non-zero exit status and create a crash report in the top level of | |
984 | the Git repository it was importing into. Crash reports contain | |
985 | a snapshot of the internal fast-import state as well as the most | |
986 | recent commands that lead up to the crash. | |
987 | ||
988 | All recent commands (including stream comments, file changes and | |
989 | progress commands) are shown in the command history within the crash | |
990 | report, but raw file data and commit messages are excluded from the | |
991 | crash report. This exclusion saves space within the report file | |
992 | and reduces the amount of buffering that fast-import must perform | |
993 | during execution. | |
994 | ||
995 | After writing a crash report fast-import will close the current | |
996 | packfile and export the marks table. This allows the frontend | |
997 | developer to inspect the repository state and resume the import from | |
998 | the point where it crashed. The modified branches and tags are not | |
999 | updated during a crash, as the import did not complete successfully. | |
1000 | Branch and tag information can be found in the crash report and | |
1001 | must be applied manually if the update is needed. | |
1002 | ||
1003 | An example crash: | |
1004 | ||
1005 | ==== | |
1006 | $ cat >in <<END_OF_INPUT | |
1007 | # my very first test commit | |
1008 | commit refs/heads/master | |
1009 | committer Shawn O. Pearce <spearce> 19283 -0400 | |
1010 | # who is that guy anyway? | |
1011 | data <<EOF | |
1012 | this is my commit | |
1013 | EOF | |
1014 | M 644 inline .gitignore | |
1015 | data <<EOF | |
1016 | .gitignore | |
1017 | EOF | |
1018 | M 777 inline bob | |
1019 | END_OF_INPUT | |
1020 | ||
b1889c36 | 1021 | $ git fast-import <in |
e7e5170f SP |
1022 | fatal: Corrupt mode: M 777 inline bob |
1023 | fast-import: dumping crash report to .git/fast_import_crash_8434 | |
1024 | ||
1025 | $ cat .git/fast_import_crash_8434 | |
1026 | fast-import crash report: | |
1027 | fast-import process: 8434 | |
1028 | parent process : 1391 | |
1029 | at Sat Sep 1 00:58:12 2007 | |
1030 | ||
1031 | fatal: Corrupt mode: M 777 inline bob | |
1032 | ||
1033 | Most Recent Commands Before Crash | |
1034 | --------------------------------- | |
1035 | # my very first test commit | |
1036 | commit refs/heads/master | |
1037 | committer Shawn O. Pearce <spearce> 19283 -0400 | |
1038 | # who is that guy anyway? | |
1039 | data <<EOF | |
1040 | M 644 inline .gitignore | |
1041 | data <<EOF | |
1042 | * M 777 inline bob | |
1043 | ||
1044 | Active Branch LRU | |
1045 | ----------------- | |
1046 | active_branches = 1 cur, 5 max | |
1047 | ||
1048 | pos clock name | |
1049 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1050 | 1) 0 refs/heads/master | |
1051 | ||
1052 | Inactive Branches | |
1053 | ----------------- | |
1054 | refs/heads/master: | |
1055 | status : active loaded dirty | |
1056 | tip commit : 0000000000000000000000000000000000000000 | |
1057 | old tree : 0000000000000000000000000000000000000000 | |
1058 | cur tree : 0000000000000000000000000000000000000000 | |
1059 | commit clock: 0 | |
1060 | last pack : | |
1061 | ||
1062 | ||
1063 | ------------------- | |
1064 | END OF CRASH REPORT | |
1065 | ==== | |
1066 | ||
bdd9f424 SP |
1067 | Tips and Tricks |
1068 | --------------- | |
1069 | The following tips and tricks have been collected from various | |
882227f1 | 1070 | users of fast-import, and are offered here as suggestions. |
bdd9f424 SP |
1071 | |
1072 | Use One Mark Per Commit | |
1073 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1074 | When doing a repository conversion, use a unique mark per commit | |
1075 | (`mark :<n>`) and supply the \--export-marks option on the command | |
882227f1 | 1076 | line. fast-import will dump a file which lists every mark and the Git |
bdd9f424 SP |
1077 | object SHA-1 that corresponds to it. If the frontend can tie |
1078 | the marks back to the source repository, it is easy to verify the | |
1079 | accuracy and completeness of the import by comparing each Git | |
1080 | commit to the corresponding source revision. | |
1081 | ||
1082 | Coming from a system such as Perforce or Subversion this should be | |
882227f1 | 1083 | quite simple, as the fast-import mark can also be the Perforce changeset |
bdd9f424 SP |
1084 | number or the Subversion revision number. |
1085 | ||
1086 | Freely Skip Around Branches | |
1087 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1088 | Don't bother trying to optimize the frontend to stick to one branch | |
1089 | at a time during an import. Although doing so might be slightly | |
882227f1 | 1090 | faster for fast-import, it tends to increase the complexity of the frontend |
bdd9f424 SP |
1091 | code considerably. |
1092 | ||
882227f1 | 1093 | The branch LRU builtin to fast-import tends to behave very well, and the |
bdd9f424 SP |
1094 | cost of activating an inactive branch is so low that bouncing around |
1095 | between branches has virtually no impact on import performance. | |
1096 | ||
c7346156 SP |
1097 | Handling Renames |
1098 | ~~~~~~~~~~~~~~~~ | |
1099 | When importing a renamed file or directory, simply delete the old | |
1100 | name(s) and modify the new name(s) during the corresponding commit. | |
1101 | Git performs rename detection after-the-fact, rather than explicitly | |
1102 | during a commit. | |
1103 | ||
bdd9f424 SP |
1104 | Use Tag Fixup Branches |
1105 | ~~~~~~~~~~~~~~~~~~~~~~ | |
1106 | Some other SCM systems let the user create a tag from multiple | |
1107 | files which are not from the same commit/changeset. Or to create | |
1108 | tags which are a subset of the files available in the repository. | |
1109 | ||
1110 | Importing these tags as-is in Git is impossible without making at | |
1111 | least one commit which ``fixes up'' the files to match the content | |
882227f1 | 1112 | of the tag. Use fast-import's `reset` command to reset a dummy branch |
bdd9f424 SP |
1113 | outside of your normal branch space to the base commit for the tag, |
1114 | then commit one or more file fixup commits, and finally tag the | |
1115 | dummy branch. | |
1116 | ||
1117 | For example since all normal branches are stored under `refs/heads/` | |
1118 | name the tag fixup branch `TAG_FIXUP`. This way it is impossible for | |
1119 | the fixup branch used by the importer to have namespace conflicts | |
1120 | with real branches imported from the source (the name `TAG_FIXUP` | |
1121 | is not `refs/heads/TAG_FIXUP`). | |
1122 | ||
1123 | When committing fixups, consider using `merge` to connect the | |
1124 | commit(s) which are supplying file revisions to the fixup branch. | |
0b444cdb | 1125 | Doing so will allow tools such as 'git blame' to track |
bdd9f424 SP |
1126 | through the real commit history and properly annotate the source |
1127 | files. | |
1128 | ||
882227f1 | 1129 | After fast-import terminates the frontend will need to do `rm .git/TAG_FIXUP` |
bdd9f424 SP |
1130 | to remove the dummy branch. |
1131 | ||
1132 | Import Now, Repack Later | |
1133 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
882227f1 | 1134 | As soon as fast-import completes the Git repository is completely valid |
02783075 | 1135 | and ready for use. Typically this takes only a very short time, |
bdd9f424 SP |
1136 | even for considerably large projects (100,000+ commits). |
1137 | ||
1138 | However repacking the repository is necessary to improve data | |
1139 | locality and access performance. It can also take hours on extremely | |
1140 | large projects (especially if -f and a large \--window parameter is | |
1141 | used). Since repacking is safe to run alongside readers and writers, | |
1142 | run the repack in the background and let it finish when it finishes. | |
1143 | There is no reason to wait to explore your new Git project! | |
1144 | ||
1145 | If you choose to wait for the repack, don't try to run benchmarks | |
882227f1 | 1146 | or performance tests until repacking is completed. fast-import outputs |
bdd9f424 SP |
1147 | suboptimal packfiles that are simply never seen in real use |
1148 | situations. | |
1149 | ||
1150 | Repacking Historical Data | |
1151 | ~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1152 | If you are repacking very old imported data (e.g. older than the | |
1153 | last year), consider expending some extra CPU time and supplying | |
0b444cdb | 1154 | \--window=50 (or higher) when you run 'git repack'. |
bdd9f424 SP |
1155 | This will take longer, but will also produce a smaller packfile. |
1156 | You only need to expend the effort once, and everyone using your | |
1157 | project will benefit from the smaller repository. | |
1158 | ||
ac053c02 SP |
1159 | Include Some Progress Messages |
1160 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1161 | Every once in a while have your frontend emit a `progress` message | |
1162 | to fast-import. The contents of the messages are entirely free-form, | |
1163 | so one suggestion would be to output the current month and year | |
1164 | each time the current commit date moves into the next month. | |
1165 | Your users will feel better knowing how much of the data stream | |
1166 | has been processed. | |
1167 | ||
bdd9f424 | 1168 | |
6e411d20 SP |
1169 | Packfile Optimization |
1170 | --------------------- | |
882227f1 | 1171 | When packing a blob fast-import always attempts to deltify against the last |
6e411d20 SP |
1172 | blob written. Unless specifically arranged for by the frontend, |
1173 | this will probably not be a prior version of the same file, so the | |
1174 | generated delta will not be the smallest possible. The resulting | |
1175 | packfile will be compressed, but will not be optimal. | |
1176 | ||
1177 | Frontends which have efficient access to all revisions of a | |
1178 | single file (for example reading an RCS/CVS ,v file) can choose | |
1179 | to supply all revisions of that file as a sequence of consecutive | |
882227f1 | 1180 | `blob` commands. This allows fast-import to deltify the different file |
6e411d20 SP |
1181 | revisions against each other, saving space in the final packfile. |
1182 | Marks can be used to later identify individual file revisions during | |
1183 | a sequence of `commit` commands. | |
1184 | ||
882227f1 SP |
1185 | The packfile(s) created by fast-import do not encourage good disk access |
1186 | patterns. This is caused by fast-import writing the data in the order | |
6e411d20 SP |
1187 | it is received on standard input, while Git typically organizes |
1188 | data within packfiles to make the most recent (current tip) data | |
1189 | appear before historical data. Git also clusters commits together, | |
1190 | speeding up revision traversal through better cache locality. | |
1191 | ||
1192 | For this reason it is strongly recommended that users repack the | |
882227f1 | 1193 | repository with `git repack -a -d` after fast-import completes, allowing |
6e411d20 SP |
1194 | Git to reorganize the packfiles for faster data access. If blob |
1195 | deltas are suboptimal (see above) then also adding the `-f` option | |
1196 | to force recomputation of all deltas can significantly reduce the | |
1197 | final packfile size (30-50% smaller can be quite typical). | |
1198 | ||
bdd9f424 | 1199 | |
6e411d20 SP |
1200 | Memory Utilization |
1201 | ------------------ | |
882227f1 | 1202 | There are a number of factors which affect how much memory fast-import |
6e411d20 | 1203 | requires to perform an import. Like critical sections of core |
02783075 BH |
1204 | Git, fast-import uses its own memory allocators to amortize any overheads |
1205 | associated with malloc. In practice fast-import tends to amortize any | |
6e411d20 SP |
1206 | malloc overheads to 0, due to its use of large block allocations. |
1207 | ||
1208 | per object | |
1209 | ~~~~~~~~~~ | |
882227f1 | 1210 | fast-import maintains an in-memory structure for every object written in |
6e411d20 SP |
1211 | this execution. On a 32 bit system the structure is 32 bytes, |
1212 | on a 64 bit system the structure is 40 bytes (due to the larger | |
1213 | pointer sizes). Objects in the table are not deallocated until | |
882227f1 | 1214 | fast-import terminates. Importing 2 million objects on a 32 bit system |
6e411d20 SP |
1215 | will require approximately 64 MiB of memory. |
1216 | ||
1217 | The object table is actually a hashtable keyed on the object name | |
882227f1 | 1218 | (the unique SHA-1). This storage configuration allows fast-import to reuse |
6e411d20 SP |
1219 | an existing or already written object and avoid writing duplicates |
1220 | to the output packfile. Duplicate blobs are surprisingly common | |
1221 | in an import, typically due to branch merges in the source. | |
1222 | ||
1223 | per mark | |
1224 | ~~~~~~~~ | |
1225 | Marks are stored in a sparse array, using 1 pointer (4 bytes or 8 | |
1226 | bytes, depending on pointer size) per mark. Although the array | |
1227 | is sparse, frontends are still strongly encouraged to use marks | |
1228 | between 1 and n, where n is the total number of marks required for | |
1229 | this import. | |
1230 | ||
1231 | per branch | |
1232 | ~~~~~~~~~~ | |
1233 | Branches are classified as active and inactive. The memory usage | |
1234 | of the two classes is significantly different. | |
1235 | ||
1236 | Inactive branches are stored in a structure which uses 96 or 120 | |
1237 | bytes (32 bit or 64 bit systems, respectively), plus the length of | |
882227f1 | 1238 | the branch name (typically under 200 bytes), per branch. fast-import will |
6e411d20 SP |
1239 | easily handle as many as 10,000 inactive branches in under 2 MiB |
1240 | of memory. | |
1241 | ||
1242 | Active branches have the same overhead as inactive branches, but | |
1243 | also contain copies of every tree that has been recently modified on | |
1244 | that branch. If subtree `include` has not been modified since the | |
1245 | branch became active, its contents will not be loaded into memory, | |
1246 | but if subtree `src` has been modified by a commit since the branch | |
1247 | became active, then its contents will be loaded in memory. | |
1248 | ||
1249 | As active branches store metadata about the files contained on that | |
1250 | branch, their in-memory storage size can grow to a considerable size | |
1251 | (see below). | |
1252 | ||
882227f1 | 1253 | fast-import automatically moves active branches to inactive status based on |
6e411d20 SP |
1254 | a simple least-recently-used algorithm. The LRU chain is updated on |
1255 | each `commit` command. The maximum number of active branches can be | |
c499d768 | 1256 | increased or decreased on the command line with \--active-branches=. |
6e411d20 SP |
1257 | |
1258 | per active tree | |
1259 | ~~~~~~~~~~~~~~~ | |
1260 | Trees (aka directories) use just 12 bytes of memory on top of the | |
1261 | memory required for their entries (see ``per active file'' below). | |
02783075 | 1262 | The cost of a tree is virtually 0, as its overhead amortizes out |
6e411d20 SP |
1263 | over the individual file entries. |
1264 | ||
1265 | per active file entry | |
1266 | ~~~~~~~~~~~~~~~~~~~~~ | |
1267 | Files (and pointers to subtrees) within active trees require 52 or 64 | |
1268 | bytes (32/64 bit platforms) per entry. To conserve space, file and | |
1269 | tree names are pooled in a common string table, allowing the filename | |
1270 | ``Makefile'' to use just 16 bytes (after including the string header | |
1271 | overhead) no matter how many times it occurs within the project. | |
1272 | ||
1273 | The active branch LRU, when coupled with the filename string pool | |
882227f1 | 1274 | and lazy loading of subtrees, allows fast-import to efficiently import |
6e411d20 SP |
1275 | projects with 2,000+ branches and 45,114+ files in a very limited |
1276 | memory footprint (less than 2.7 MiB per active branch). | |
1277 | ||
dc01f59d JN |
1278 | Signals |
1279 | ------- | |
1280 | Sending *SIGUSR1* to the 'git fast-import' process ends the current | |
1281 | packfile early, simulating a `checkpoint` command. The impatient | |
1282 | operator can use this facility to peek at the objects and refs from an | |
1283 | import in progress, at the cost of some added running time and worse | |
1284 | compression. | |
6e411d20 SP |
1285 | |
1286 | Author | |
1287 | ------ | |
1288 | Written by Shawn O. Pearce <spearce@spearce.org>. | |
1289 | ||
1290 | Documentation | |
1291 | -------------- | |
1292 | Documentation by Shawn O. Pearce <spearce@spearce.org>. | |
1293 | ||
1294 | GIT | |
1295 | --- | |
9e1f0a85 | 1296 | Part of the linkgit:git[1] suite |