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<body>
<div id="header">
<h1>
git-fast-import(1) Manual Page
</h1>
<h2>NAME</h2>
<div class="sectionbody">
<p>git-fast-import -
Backend for fast Git data importers
</p>
</div>
</div>
<h2 id="_synopsis">SYNOPSIS</h2>
<div class="sectionbody">
<div class="paragraph"><p>frontend | <em>git fast-import</em> [options]</p></div>
</div>
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph"><p>This program is usually not what the end user wants to run directly.
Most end users want to use one of the existing frontend programs,
which parses a specific type of foreign source and feeds the contents
stored there to <em>git fast-import</em>.</p></div>
<div class="paragraph"><p>fast-import reads a mixed command/data stream from standard input and
writes one or more packfiles directly into the current repository.
When EOF is received on standard input, fast import writes out
updated branch and tag refs, fully updating the current repository
with the newly imported data.</p></div>
<div class="paragraph"><p>The fast-import backend itself can import into an empty repository (one that
has already been initialized by <em>git init</em>) or incrementally
update an existing populated repository. Whether or not incremental
imports are supported from a particular foreign source depends on
the frontend program in use.</p></div>
</div>
<h2 id="_options">OPTIONS</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
--date-format=<fmt>
</dt>
<dd>
<p>
Specify the type of dates the frontend will supply to
fast-import within <tt>author</tt>, <tt>committer</tt> and <tt>tagger</tt> commands.
See “Date Formats” below for details about which formats
are supported, and their syntax.
</p>
</dd>
<dt class="hdlist1">
--force
</dt>
<dd>
<p>
Force updating modified existing branches, even if doing
so would cause commits to be lost (as the new commit does
not contain the old commit).
</p>
</dd>
<dt class="hdlist1">
--max-pack-size=<n>
</dt>
<dd>
<p>
Maximum size of each output packfile.
The default is unlimited.
</p>
</dd>
<dt class="hdlist1">
--big-file-threshold=<n>
</dt>
<dd>
<p>
Maximum size of a blob that fast-import will attempt to
create a delta for, expressed in bytes. The default is 512m
(512 MiB). Some importers may wish to lower this on systems
with constrained memory.
</p>
</dd>
<dt class="hdlist1">
--depth=<n>
</dt>
<dd>
<p>
Maximum delta depth, for blob and tree deltification.
Default is 10.
</p>
</dd>
<dt class="hdlist1">
--active-branches=<n>
</dt>
<dd>
<p>
Maximum number of branches to maintain active at once.
See “Memory Utilization” below for details. Default is 5.
</p>
</dd>
<dt class="hdlist1">
--export-marks=<file>
</dt>
<dd>
<p>
Dumps the internal marks table to <file> when complete.
Marks are written one per line as <tt>:markid SHA-1</tt>.
Frontends can use this file to validate imports after they
have been completed, or to save the marks table across
incremental runs. As <file> is only opened and truncated
at checkpoint (or completion) the same path can also be
safely given to --import-marks.
</p>
</dd>
<dt class="hdlist1">
--import-marks=<file>
</dt>
<dd>
<p>
Before processing any input, load the marks specified in
<file>. The input file must exist, must be readable, and
must use the same format as produced by --export-marks.
Multiple options may be supplied to import more than one
set of marks. If a mark is defined to different values,
the last file wins.
</p>
</dd>
<dt class="hdlist1">
--relative-marks
</dt>
<dd>
<p>
After specifying --relative-marks= the paths specified
with --import-marks= and --export-marks= are relative
to an internal directory in the current repository.
In git-fast-import this means that the paths are relative
to the .git/info/fast-import directory. However, other
importers may use a different location.
</p>
</dd>
<dt class="hdlist1">
--no-relative-marks
</dt>
<dd>
<p>
Negates a previous --relative-marks. Allows for combining
relative and non-relative marks by interweaving
--(no-)-relative-marks= with the --(import|export)-marks=
options.
</p>
</dd>
<dt class="hdlist1">
--export-pack-edges=<file>
</dt>
<dd>
<p>
After creating a packfile, print a line of data to
<file> listing the filename of the packfile and the last
commit on each branch that was written to that packfile.
This information may be useful after importing projects
whose total object set exceeds the 4 GiB packfile limit,
as these commits can be used as edge points during calls
to <em>git pack-objects</em>.
</p>
</dd>
<dt class="hdlist1">
--quiet
</dt>
<dd>
<p>
Disable all non-fatal output, making fast-import silent when it
is successful. This option disables the output shown by
--stats.
</p>
</dd>
<dt class="hdlist1">
--stats
</dt>
<dd>
<p>
Display some basic statistics about the objects fast-import has
created, the packfiles they were stored into, and the
memory used by fast-import during this run. Showing this output
is currently the default, but can be disabled with --quiet.
</p>
</dd>
</dl></div>
</div>
<h2 id="_performance">Performance</h2>
<div class="sectionbody">
<div class="paragraph"><p>The design of fast-import allows it to import large projects in a minimum
amount of memory usage and processing time. Assuming the frontend
is able to keep up with fast-import and feed it a constant stream of data,
import times for projects holding 10+ years of history and containing
100,000+ individual commits are generally completed in just 1-2
hours on quite modest (~$2,000 USD) hardware.</p></div>
<div class="paragraph"><p>Most bottlenecks appear to be in foreign source data access (the
source just cannot extract revisions fast enough) or disk IO (fast-import
writes as fast as the disk will take the data). Imports will run
faster if the source data is stored on a different drive than the
destination Git repository (due to less IO contention).</p></div>
</div>
<h2 id="_development_cost">Development Cost</h2>
<div class="sectionbody">
<div class="paragraph"><p>A typical frontend for fast-import tends to weigh in at approximately 200
lines of Perl/Python/Ruby code. Most developers have been able to
create working importers in just a couple of hours, even though it
is their first exposure to fast-import, and sometimes even to Git. This is
an ideal situation, given that most conversion tools are throw-away
(use once, and never look back).</p></div>
</div>
<h2 id="_parallel_operation">Parallel Operation</h2>
<div class="sectionbody">
<div class="paragraph"><p>Like <em>git push</em> or <em>git fetch</em>, imports handled by fast-import are safe to
run alongside parallel <tt>git repack -a -d</tt> or <tt>git gc</tt> invocations,
or any other Git operation (including <em>git prune</em>, as loose objects
are never used by fast-import).</p></div>
<div class="paragraph"><p>fast-import does not lock the branch or tag refs it is actively importing.
After the import, during its ref update phase, fast-import tests each
existing branch ref to verify the update will be a fast-forward
update (the commit stored in the ref is contained in the new
history of the commit to be written). If the update is not a
fast-forward update, fast-import will skip updating that ref and instead
prints a warning message. fast-import will always attempt to update all
branch refs, and does not stop on the first failure.</p></div>
<div class="paragraph"><p>Branch updates can be forced with --force, but it’s recommended that
this only be used on an otherwise quiet repository. Using --force
is not necessary for an initial import into an empty repository.</p></div>
</div>
<h2 id="_technical_discussion">Technical Discussion</h2>
<div class="sectionbody">
<div class="paragraph"><p>fast-import tracks a set of branches in memory. Any branch can be created
or modified at any point during the import process by sending a
<tt>commit</tt> command on the input stream. This design allows a frontend
program to process an unlimited number of branches simultaneously,
generating commits in the order they are available from the source
data. It also simplifies the frontend programs considerably.</p></div>
<div class="paragraph"><p>fast-import does not use or alter the current working directory, or any
file within it. (It does however update the current Git repository,
as referenced by <tt>GIT_DIR</tt>.) Therefore an import frontend may use
the working directory for its own purposes, such as extracting file
revisions from the foreign source. This ignorance of the working
directory also allows fast-import to run very quickly, as it does not
need to perform any costly file update operations when switching
between branches.</p></div>
</div>
<h2 id="_input_format">Input Format</h2>
<div class="sectionbody">
<div class="paragraph"><p>With the exception of raw file data (which Git does not interpret)
the fast-import input format is text (ASCII) based. This text based
format simplifies development and debugging of frontend programs,
especially when a higher level language such as Perl, Python or
Ruby is being used.</p></div>
<div class="paragraph"><p>fast-import is very strict about its input. Where we say SP below we mean
<strong>exactly</strong> one space. Likewise LF means one (and only one) linefeed.
Supplying additional whitespace characters will cause unexpected
results, such as branch names or file names with leading or trailing
spaces in their name, or early termination of fast-import when it encounters
unexpected input.</p></div>
<h3 id="_stream_comments">Stream Comments</h3><div style="clear:left"></div>
<div class="paragraph"><p>To aid in debugging frontends fast-import ignores any line that
begins with <tt>#</tt> (ASCII pound/hash) up to and including the line
ending <tt>LF</tt>. A comment line may contain any sequence of bytes
that does not contain an LF and therefore may be used to include
any detailed debugging information that might be specific to the
frontend and useful when inspecting a fast-import data stream.</p></div>
<h3 id="_date_formats">Date Formats</h3><div style="clear:left"></div>
<div class="paragraph"><p>The following date formats are supported. A frontend should select
the format it will use for this import by passing the format name
in the --date-format=<fmt> command line option.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<tt>raw</tt>
</dt>
<dd>
<p>
This is the Git native format and is <tt><time> SP <offutc></tt>.
It is also fast-import’s default format, if --date-format was
not specified.
</p>
<div class="paragraph"><p>The time of the event is specified by <tt><time></tt> as the number of
seconds since the UNIX epoch (midnight, Jan 1, 1970, UTC) and is
written as an ASCII decimal integer.</p></div>
<div class="paragraph"><p>The local offset is specified by <tt><offutc></tt> as a positive or negative
offset from UTC. For example EST (which is 5 hours behind UTC)
would be expressed in <tt><tz></tt> by “-0500” while UTC is “+0000”.
The local offset does not affect <tt><time></tt>; it is used only as an
advisement to help formatting routines display the timestamp.</p></div>
<div class="paragraph"><p>If the local offset is not available in the source material, use
“+0000”, or the most common local offset. For example many
organizations have a CVS repository which has only ever been accessed
by users who are located in the same location and timezone. In this
case a reasonable offset from UTC could be assumed.</p></div>
<div class="paragraph"><p>Unlike the <tt>rfc2822</tt> format, this format is very strict. Any
variation in formatting will cause fast-import to reject the value.</p></div>
</dd>
<dt class="hdlist1">
<tt>rfc2822</tt>
</dt>
<dd>
<p>
This is the standard email format as described by RFC 2822.
</p>
<div class="paragraph"><p>An example value is “Tue Feb 6 11:22:18 2007 -0500”. The Git
parser is accurate, but a little on the lenient side. It is the
same parser used by <em>git am</em> when applying patches
received from email.</p></div>
<div class="paragraph"><p>Some malformed strings may be accepted as valid dates. In some of
these cases Git will still be able to obtain the correct date from
the malformed string. There are also some types of malformed
strings which Git will parse wrong, and yet consider valid.
Seriously malformed strings will be rejected.</p></div>
<div class="paragraph"><p>Unlike the <tt>raw</tt> format above, the timezone/UTC offset information
contained in an RFC 2822 date string is used to adjust the date
value to UTC prior to storage. Therefore it is important that
this information be as accurate as possible.</p></div>
<div class="paragraph"><p>If the source material uses RFC 2822 style dates,
the frontend should let fast-import handle the parsing and conversion
(rather than attempting to do it itself) as the Git parser has
been well tested in the wild.</p></div>
<div class="paragraph"><p>Frontends should prefer the <tt>raw</tt> format if the source material
already uses UNIX-epoch format, can be coaxed to give dates in that
format, or its format is easily convertible to it, as there is no
ambiguity in parsing.</p></div>
</dd>
<dt class="hdlist1">
<tt>now</tt>
</dt>
<dd>
<p>
Always use the current time and timezone. The literal
<tt>now</tt> must always be supplied for <tt><when></tt>.
</p>
<div class="paragraph"><p>This is a toy format. The current time and timezone of this system
is always copied into the identity string at the time it is being
created by fast-import. There is no way to specify a different time or
timezone.</p></div>
<div class="paragraph"><p>This particular format is supplied as it’s short to implement and
may be useful to a process that wants to create a new commit
right now, without needing to use a working directory or
<em>git update-index</em>.</p></div>
<div class="paragraph"><p>If separate <tt>author</tt> and <tt>committer</tt> commands are used in a <tt>commit</tt>
the timestamps may not match, as the system clock will be polled
twice (once for each command). The only way to ensure that both
author and committer identity information has the same timestamp
is to omit <tt>author</tt> (thus copying from <tt>committer</tt>) or to use a
date format other than <tt>now</tt>.</p></div>
</dd>
</dl></div>
<h3 id="_commands">Commands</h3><div style="clear:left"></div>
<div class="paragraph"><p>fast-import accepts several commands to update the current repository
and control the current import process. More detailed discussion
(with examples) of each command follows later.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<tt>commit</tt>
</dt>
<dd>
<p>
Creates a new branch or updates an existing branch by
creating a new commit and updating the branch to point at
the newly created commit.
</p>
</dd>
<dt class="hdlist1">
<tt>tag</tt>
</dt>
<dd>
<p>
Creates an annotated tag object from an existing commit or
branch. Lightweight tags are not supported by this command,
as they are not recommended for recording meaningful points
in time.
</p>
</dd>
<dt class="hdlist1">
<tt>reset</tt>
</dt>
<dd>
<p>
Reset an existing branch (or a new branch) to a specific
revision. This command must be used to change a branch to
a specific revision without making a commit on it.
</p>
</dd>
<dt class="hdlist1">
<tt>blob</tt>
</dt>
<dd>
<p>
Convert raw file data into a blob, for future use in a
<tt>commit</tt> command. This command is optional and is not
needed to perform an import.
</p>
</dd>
<dt class="hdlist1">
<tt>checkpoint</tt>
</dt>
<dd>
<p>
Forces fast-import to close the current packfile, generate its
unique SHA-1 checksum and index, and start a new packfile.
This command is optional and is not needed to perform
an import.
</p>
</dd>
<dt class="hdlist1">
<tt>progress</tt>
</dt>
<dd>
<p>
Causes fast-import to echo the entire line to its own
standard output. This command is optional and is not needed
to perform an import.
</p>
</dd>
<dt class="hdlist1">
<tt>feature</tt>
</dt>
<dd>
<p>
Require that fast-import supports the specified feature, or
abort if it does not.
</p>
</dd>
<dt class="hdlist1">
<tt>option</tt>
</dt>
<dd>
<p>
Specify any of the options listed under OPTIONS that do not
change stream semantic to suit the frontend’s needs. This
command is optional and is not needed to perform an import.
</p>
</dd>
</dl></div>
<h3 id="_tt_commit_tt"><tt>commit</tt></h3><div style="clear:left"></div>
<div class="paragraph"><p>Create or update a branch with a new commit, recording one logical
change to the project.</p></div>
<div class="literalblock">
<div class="content">
<pre><tt> 'commit' SP <ref> LF
mark?
('author' (SP <name>)? SP LT <email> GT SP <when> LF)?
'committer' (SP <name>)? SP LT <email> GT SP <when> LF
data
('from' SP <committish> LF)?
('merge' SP <committish> LF)?
(filemodify | filedelete | filecopy | filerename | filedeleteall | notemodify)*
LF?</tt></pre>
</div></div>
<div class="paragraph"><p>where <tt><ref></tt> is the name of the branch to make the commit on.
Typically branch names are prefixed with <tt>refs/heads/</tt> in
Git, so importing the CVS branch symbol <tt>RELENG-1_0</tt> would use
<tt>refs/heads/RELENG-1_0</tt> for the value of <tt><ref></tt>. The value of
<tt><ref></tt> must be a valid refname in Git. As <tt>LF</tt> is not valid in
a Git refname, no quoting or escaping syntax is supported here.</p></div>
<div class="paragraph"><p>A <tt>mark</tt> command may optionally appear, requesting fast-import to save a
reference to the newly created commit for future use by the frontend
(see below for format). It is very common for frontends to mark
every commit they create, thereby allowing future branch creation
from any imported commit.</p></div>
<div class="paragraph"><p>The <tt>data</tt> command following <tt>committer</tt> must supply the commit
message (see below for <tt>data</tt> command syntax). To import an empty
commit message use a 0 length data. Commit messages are free-form
and are not interpreted by Git. Currently they must be encoded in
UTF-8, as fast-import does not permit other encodings to be specified.</p></div>
<div class="paragraph"><p>Zero or more <tt>filemodify</tt>, <tt>filedelete</tt>, <tt>filecopy</tt>, <tt>filerename</tt>,
<tt>filedeleteall</tt> and <tt>notemodify</tt> commands
may be included to update the contents of the branch prior to
creating the commit. These commands may be supplied in any order.
However it is recommended that a <tt>filedeleteall</tt> command precede
all <tt>filemodify</tt>, <tt>filecopy</tt>, <tt>filerename</tt> and <tt>notemodify</tt> commands in
the same commit, as <tt>filedeleteall</tt> wipes the branch clean (see below).</p></div>
<div class="paragraph"><p>The <tt>LF</tt> after the command is optional (it used to be required).</p></div>
<h4 id="_tt_author_tt"><tt>author</tt></h4>
<div class="paragraph"><p>An <tt>author</tt> command may optionally appear, if the author information
might differ from the committer information. If <tt>author</tt> is omitted
then fast-import will automatically use the committer’s information for
the author portion of the commit. See below for a description of
the fields in <tt>author</tt>, as they are identical to <tt>committer</tt>.</p></div>
<h4 id="_tt_committer_tt"><tt>committer</tt></h4>
<div class="paragraph"><p>The <tt>committer</tt> command indicates who made this commit, and when
they made it.</p></div>
<div class="paragraph"><p>Here <tt><name></tt> is the person’s display name (for example
“Com M Itter”) and <tt><email></tt> is the person’s email address
(“<a href="mailto:[email protected]">[email protected]</a>”). <tt>LT</tt> and <tt>GT</tt> are the literal less-than (\x3c)
and greater-than (\x3e) symbols. These are required to delimit
the email address from the other fields in the line. Note that
<tt><name></tt> is free-form and may contain any sequence of bytes, except
<tt>LT</tt> and <tt>LF</tt>. It is typically UTF-8 encoded.</p></div>
<div class="paragraph"><p>The time of the change is specified by <tt><when></tt> using the date format
that was selected by the --date-format=<fmt> command line option.
See “Date Formats” above for the set of supported formats, and
their syntax.</p></div>
<h4 id="_tt_from_tt"><tt>from</tt></h4>
<div class="paragraph"><p>The <tt>from</tt> command is used to specify the commit to initialize
this branch from. This revision will be the first ancestor of the
new commit.</p></div>
<div class="paragraph"><p>Omitting the <tt>from</tt> command in the first commit of a new branch
will cause fast-import to create that commit with no ancestor. This
tends to be desired only for the initial commit of a project.
If the frontend creates all files from scratch when making a new
branch, a <tt>merge</tt> command may be used instead of <tt>from</tt> to start
the commit with an empty tree.
Omitting the <tt>from</tt> command on existing branches is usually desired,
as the current commit on that branch is automatically assumed to
be the first ancestor of the new commit.</p></div>
<div class="paragraph"><p>As <tt>LF</tt> is not valid in a Git refname or SHA-1 expression, no
quoting or escaping syntax is supported within <tt><committish></tt>.</p></div>
<div class="paragraph"><p>Here <tt><committish></tt> is any of the following:</p></div>
<div class="ulist"><ul>
<li>
<p>
The name of an existing branch already in fast-import’s internal branch
table. If fast-import doesn’t know the name, it’s treated as a SHA-1
expression.
</p>
</li>
<li>
<p>
A mark reference, <tt>:<idnum></tt>, where <tt><idnum></tt> is the mark number.
</p>
<div class="paragraph"><p>The reason fast-import uses <tt>:</tt> to denote a mark reference is this character
is not legal in a Git branch name. The leading <tt>:</tt> makes it easy
to distinguish between the mark 42 (<tt>:42</tt>) and the branch 42 (<tt>42</tt>
or <tt>refs/heads/42</tt>), or an abbreviated SHA-1 which happened to
consist only of base-10 digits.</p></div>
<div class="paragraph"><p>Marks must be declared (via <tt>mark</tt>) before they can be used.</p></div>
</li>
<li>
<p>
A complete 40 byte or abbreviated commit SHA-1 in hex.
</p>
</li>
<li>
<p>
Any valid Git SHA-1 expression that resolves to a commit. See
“SPECIFYING REVISIONS” in <a href="gitrevisions.html">gitrevisions(7)</a> for details.
</p>
</li>
</ul></div>
<div class="paragraph"><p>The special case of restarting an incremental import from the
current branch value should be written as:</p></div>
<div class="listingblock">
<div class="content">
<pre><tt> from refs/heads/branch^0</tt></pre>
</div></div>
<div class="paragraph"><p>The <tt>^0</tt> suffix is necessary as fast-import does not permit a branch to
start from itself, and the branch is created in memory before the
<tt>from</tt> command is even read from the input. Adding <tt>^0</tt> will force
fast-import to resolve the commit through Git’s revision parsing library,
rather than its internal branch table, thereby loading in the
existing value of the branch.</p></div>
<h4 id="_tt_merge_tt"><tt>merge</tt></h4>
<div class="paragraph"><p>Includes one additional ancestor commit. If the <tt>from</tt> command is
omitted when creating a new branch, the first <tt>merge</tt> commit will be
the first ancestor of the current commit, and the branch will start
out with no files. An unlimited number of <tt>merge</tt> commands per
commit are permitted by fast-import, thereby establishing an n-way merge.
However Git’s other tools never create commits with more than 15
additional ancestors (forming a 16-way merge). For this reason
it is suggested that frontends do not use more than 15 <tt>merge</tt>
commands per commit; 16, if starting a new, empty branch.</p></div>
<div class="paragraph"><p>Here <tt><committish></tt> is any of the commit specification expressions
also accepted by <tt>from</tt> (see above).</p></div>
<h4 id="_tt_filemodify_tt"><tt>filemodify</tt></h4>
<div class="paragraph"><p>Included in a <tt>commit</tt> command to add a new file or change the
content of an existing file. This command has two different means
of specifying the content of the file.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
External data format
</dt>
<dd>
<p>
The data content for the file was already supplied by a prior
<tt>blob</tt> command. The frontend just needs to connect it.
</p>
<div class="literalblock">
<div class="content">
<pre><tt> 'M' SP <mode> SP <dataref> SP <path> LF</tt></pre>
</div></div>
<div class="paragraph"><p>Here usually <tt><dataref></tt> must be either a mark reference (<tt>:<idnum></tt>)
set by a prior <tt>blob</tt> command, or a full 40-byte SHA-1 of an
existing Git blob object. If <tt><mode></tt> is <tt>040000</tt>` then
<tt><dataref></tt> must be the full 40-byte SHA-1 of an existing
Git tree object or a mark reference set with <tt>--import-marks</tt>.</p></div>
</dd>
<dt class="hdlist1">
Inline data format
</dt>
<dd>
<p>
The data content for the file has not been supplied yet.
The frontend wants to supply it as part of this modify
command.
</p>
<div class="literalblock">
<div class="content">
<pre><tt> 'M' SP <mode> SP 'inline' SP <path> LF
data</tt></pre>
</div></div>