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GIT-FAST-IMPORT(1)		  Git Manual		    GIT-FAST-IMPORT(1)

NAME
       git-fast-import - Backend for fast Git data importers

SYNOPSIS
       frontend	| git fast-import [options]

DESCRIPTION
       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	git fast-import.

       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.

       The fast-import backend itself can import into an empty repository (one
       that has	already	been initialized by git	init) 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.

OPTIONS
       --force
	   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).

       --quiet
	   Disable all non-fatal output, making	fast-import silent when	it is
	   successful. This option disables the	output shown by	--stats.

       --stats
	   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.

   Options for Frontends
       --cat-blob-fd=<fd>
	   Write responses to get-mark,	cat-blob, and ls queries to the	file
	   descriptor <fd> instead of stdout. Allows progress output intended
	   for the end-user to be separated from other output.

       --date-format=<fmt>
	   Specify the type of dates the frontend will supply to fast-import
	   within author, committer and	tagger commands. See "Date Formats"
	   below for details about which formats are supported,	and their
	   syntax.

       --done
	   Terminate with error	if there is no done command at the end of the
	   stream. This	option might be	useful for detecting errors that cause
	   the frontend	to terminate before it has started to write a stream.

   Locations of	Marks Files
       --export-marks=<file>
	   Dumps the internal marks table to <file> when complete. Marks are
	   written one per line	as :markid SHA-1. 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.

       --import-marks=<file>
	   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.

       --import-marks-if-exists=<file>
	   Like	--import-marks but instead of erroring out, silently skips the
	   file	if it does not exist.

       --[no-]relative-marks
	   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.

	   Relative and	non-relative marks may be combined by interweaving
	   --(no-)-relative-marks with the --(import|export)-marks= options.

   Performance and Compression Tuning
       --active-branches=<n>
	   Maximum number of branches to maintain active at once. See "Memory
	   Utilization"	below for details. Default is 5.

       --big-file-threshold=<n>
	   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.

       --depth=<n>
	   Maximum delta depth,	for blob and tree deltification. Default is
	   10.

       --export-pack-edges=<file>
	   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 git	pack-objects.

       --max-pack-size=<n>
	   Maximum size	of each	output packfile. The default is	unlimited.

       fastimport.unpackLimit
	   See git-config(1)

PERFORMANCE
       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.

       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).

DEVELOPMENT COST
       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).

PARALLEL OPERATION
       Like git	push or	git fetch, imports handled by fast-import are safe to
       run alongside parallel git repack -a -d or git gc invocations, or any
       other Git operation (including git prune, as loose objects are never
       used by fast-import).

       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.

       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.

TECHNICAL DISCUSSION
       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
       commit 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.

       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 GIT_DIR.) 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.

INPUT FORMAT
       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.

       fast-import is very strict about	its input. Where we say	SP below we
       mean exactly one	space. Likewise	LF means one (and only one) linefeed
       and HT one (and only one) horizontal tab. 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.

   Stream Comments
       To aid in debugging frontends fast-import ignores any line that begins
       with # (ASCII pound/hash) up to and including the line ending LF. 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.

   Date	Formats
       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.

       raw
	   This	is the Git native format and is	<time> SP <offutc>. It is also
	   fast-import's default format, if --date-format was not specified.

	   The time of the event is specified by <time>	as the number of
	   seconds since the UNIX epoch	(midnight, Jan 1, 1970,	UTC) and is
	   written as an ASCII decimal integer.

	   The local offset is specified by <offutc> as	a positive or negative
	   offset from UTC. For	example	EST (which is 5	hours behind UTC)
	   would be expressed in <tz> by "-0500" while UTC is "+0000". The
	   local offset	does not affect	<time>;	it is used only	as an
	   advisement to help formatting routines display the timestamp.

	   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 time
	   zone. In this case a	reasonable offset from UTC could be assumed.

	   Unlike the rfc2822 format, this format is very strict. Any
	   variation in	formatting will	cause fast-import to reject the	value.

       rfc2822
	   This	is the standard	email format as	described by RFC 2822.

	   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 git am when applying patches received	from email.

	   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.

	   Unlike the raw format above,	the time zone/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.

	   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.

	   Frontends should prefer the raw 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.

       now
	   Always use the current time and time	zone. The literal now must
	   always be supplied for <when>.

	   This	is a toy format. The current time and time zone	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 time zone.

	   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 git
	   update-index.

	   If separate author and committer commands are used in a commit 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	author (thus copying from committer) or	to use a date format
	   other than now.

   Commands
       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.

       commit
	   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.

       tag
	   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.

       reset
	   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.

       blob
	   Convert raw file data into a	blob, for future use in	a commit
	   command. This command is optional and is not	needed to perform an
	   import.

       checkpoint
	   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.

       progress
	   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.

       done
	   Marks the end of the	stream.	This command is	optional unless	the
	   done	feature	was requested using the	--done command-line option or
	   feature done	command.

       get-mark
	   Causes fast-import to print the SHA-1 corresponding to a mark to
	   the file descriptor set with	--cat-blob-fd, or stdout if
	   unspecified.

       cat-blob
	   Causes fast-import to print a blob in cat-file --batch format to
	   the file descriptor set with	--cat-blob-fd or stdout	if
	   unspecified.

       ls
	   Causes fast-import to print a line describing a directory entry in
	   ls-tree format to the file descriptor set with --cat-blob-fd	or
	   stdout if unspecified.

       feature
	   Enable the specified	feature. This requires that fast-import
	   supports the	specified feature, and aborts if it does not.

       option
	   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.

   commit
       Create or update	a branch with a	new commit, recording one logical
       change to the project.

		   '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 <commit-ish> LF)?
		   ('merge' SP <commit-ish> LF)?
		   (filemodify | filedelete | filecopy | filerename | filedeleteall | notemodify)*
		   LF?

       where <ref> is the name of the branch to	make the commit	on. Typically
       branch names are	prefixed with refs/heads/ in Git, so importing the CVS
       branch symbol RELENG-1_0	would use refs/heads/RELENG-1_0	for the	value
       of <ref>. The value of <ref> must be a valid refname in Git. As LF is
       not valid in a Git refname, no quoting or escaping syntax is supported
       here.

       A mark 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.

       The data	command	following committer must supply	the commit message
       (see below for data 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.

       Zero or more filemodify,	filedelete, filecopy, filerename,
       filedeleteall and notemodify 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
       filedeleteall command precede all filemodify, filecopy, filerename and
       notemodify commands in the same commit, as filedeleteall	wipes the
       branch clean (see below).

       The LF after the	command	is optional (it	used to	be required).

       author
	   An author command may optionally appear, if the author information
	   might differ	from the committer information.	If author 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 author, as they are	identical to committer.

       committer
	   The committer command indicates who made this commit, and when they
	   made	it.

	   Here	<name> is the person's display name (for example "Com M
	   Itter") and <email> is the person's email address
	   ("cm@example.com"). LT and GT 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 <name>
	   and <email> are free-form and may contain any sequence of bytes,
	   except LT, GT and LF. <name>	is typically UTF-8 encoded.

	   The time of the change is specified by <when> 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.

       from
	   The from command is used to specify the commit to initialize	this
	   branch from.	This revision will be the first	ancestor of the	new
	   commit. The state of	the tree built at this commit will begin with
	   the state at	the from commit, and be	altered	by the content
	   modifications in this commit.

	   Omitting the	from 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 merge command may be used instead of from to start	the
	   commit with an empty	tree. Omitting the from	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.

	   As LF is not	valid in a Git refname or SHA-1	expression, no quoting
	   or escaping syntax is supported within <commit-ish>.

	   Here	<commit-ish> is	any of the following:

	   o   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.

	   o   A mark reference, :<idnum>, where <idnum> is the	mark number.

	       The reason fast-import uses : to	denote a mark reference	is
	       this character is not legal in a	Git branch name. The leading :
	       makes it	easy to	distinguish between the	mark 42	(:42) and the
	       branch 42 (42 or	refs/heads/42),	or an abbreviated SHA-1	which
	       happened	to consist only	of base-10 digits.

	       Marks must be declared (via mark) before	they can be used.

	   o   A complete 40 byte or abbreviated commit	SHA-1 in hex.

	   o   Any valid Git SHA-1 expression that resolves to a commit. See
	       "SPECIFYING REVISIONS" in gitrevisions(7) for details.

	   o   The special null	SHA-1 (40 zeros) specifies that	the branch is
	       to be removed.

	   The special case of restarting an incremental import	from the
	   current branch value	should be written as:

		       from refs/heads/branch^0

	   The ^0 suffix is necessary as fast-import does not permit a branch
	   to start from itself, and the branch	is created in memory before
	   the from command is even read from the input. Adding	^0 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.

       merge
	   Includes one	additional ancestor commit. The	additional ancestry
	   link	does not change	the way	the tree state is built	at this
	   commit. If the from command is omitted when creating	a new branch,
	   the first merge commit will be the first ancestor of	the current
	   commit, and the branch will start out with no files.	An unlimited
	   number of merge commands per	commit are permitted by	fast-import,
	   thereby establishing	an n-way merge.

	   Here	<commit-ish> is	any of the commit specification	expressions
	   also	accepted by from (see above).

       filemodify
	   Included in a commit	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.

	   External data format
	       The data	content	for the	file was already supplied by a prior
	       blob command. The frontend just needs to	connect	it.

			   'M' SP <mode> SP <dataref> SP <path>	LF

	       Here usually <dataref> must be either a mark reference
	       (:<idnum>) set by a prior blob command, or a full 40-byte SHA-1
	       of an existing Git blob object. If <mode> is 040000` then
	       <dataref> must be the full 40-byte SHA-1	of an existing Git
	       tree object or a	mark reference set with	--import-marks.

	   Inline data format
	       The data	content	for the	file has not been supplied yet.	The
	       frontend	wants to supply	it as part of this modify command.

			   'M' SP <mode> SP 'inline' SP	<path> LF
			   data

	       See below for a detailed	description of the data	command.

	   In both formats <mode> is the type of file entry, specified in
	   octal. Git only supports the	following modes:

	   o   100644 or 644: A	normal (not-executable)	file. The majority of
	       files in	most projects use this mode. If	in doubt, this is what
	       you want.

	   o   100755 or 755: A	normal,	but executable,	file.

	   o   120000: A symlink, the content of the file will be the link
	       target.

	   o   160000: A gitlink, SHA-1	of the object refers to	a commit in
	       another repository. Git links can only be specified by SHA or
	       through a commit	mark. They are used to implement submodules.

	   o   040000: A subdirectory. Subdirectories can only be specified by
	       SHA or through a	tree mark set with --import-marks.

	   In both formats <path> is the complete path of the file to be added
	   (if not already existing) or	modified (if already existing).

	   A <path> string must	use UNIX-style directory separators (forward
	   slash /), may contain any byte other	than LF, and must not start
	   with	double quote (").

	   A path can use C-style string quoting; this is accepted in all
	   cases and mandatory if the filename starts with double quote	or
	   contains LF.	In C-style quoting, the	complete name should be
	   surrounded with double quotes, and any LF, backslash, or double
	   quote characters must be escaped by preceding them with a backslash
	   (e.g., "path/with\n,	\\ and \" in it").

	   The value of	<path> must be in canonical form. That is it must not:

	   o   contain an empty	directory component (e.g.  foo//bar is
	       invalid),

	   o   end with	a directory separator (e.g.  foo/ is invalid),

	   o   start with a directory separator	(e.g.  /foo is invalid),

	   o   contain the special component .	or ..  (e.g.  foo/./bar	and
	       foo/../bar are invalid).

	   The root of the tree	can be represented by an empty string as
	   <path>.

	   It is recommended that <path> always	be encoded using UTF-8.

       filedelete
	   Included in a commit	command	to remove a file or recursively	delete
	   an entire directory from the	branch.	If the file or directory
	   removal makes its parent directory empty, the parent	directory will
	   be automatically removed too. This cascades up the tree until the
	   first non-empty directory or	the root is reached.

		       'D' SP <path> LF

	   here	<path> is the complete path of the file	or subdirectory	to be
	   removed from	the branch. See	filemodify above for a detailed
	   description of <path>.

       filecopy
	   Recursively copies an existing file or subdirectory to a different
	   location within the branch. The existing file or directory must
	   exist. If the destination exists it will be completely replaced by
	   the content copied from the source.

		       'C' SP <path> SP	<path> LF

	   here	the first <path> is the	source location	and the	second <path>
	   is the destination. See filemodify above for	a detailed description
	   of what <path> may look like. To use	a source path that contains SP
	   the path must be quoted.

	   A filecopy command takes effect immediately.	Once the source
	   location has	been copied to the destination any future commands
	   applied to the source location will not impact the destination of
	   the copy.

       filerename
	   Renames an existing file or subdirectory to a different location
	   within the branch. The existing file	or directory must exist. If
	   the destination exists it will be replaced by the source directory.

		       'R' SP <path> SP	<path> LF

	   here	the first <path> is the	source location	and the	second <path>
	   is the destination. See filemodify above for	a detailed description
	   of what <path> may look like. To use	a source path that contains SP
	   the path must be quoted.

	   A filerename	command	takes effect immediately. Once the source
	   location has	been renamed to	the destination	any future commands
	   applied to the source location will create new files	there and not
	   impact the destination of the rename.

	   Note	that a filerename is the same as a filecopy followed by	a
	   filedelete of the source location. There is a slight	performance
	   advantage to	using filerename, but the advantage is so small	that
	   it is never worth trying to convert a delete/add pair in source
	   material into a rename for fast-import. This	filerename command is
	   provided just to simplify frontends that already have rename
	   information and don't want bother with decomposing it into a
	   filecopy followed by	a filedelete.

       filedeleteall
	   Included in a commit	command	to remove all files (and also all
	   directories)	from the branch. This command resets the internal
	   branch structure to have no files in	it, allowing the frontend to
	   subsequently	add all	interesting files from scratch.

		       'deleteall' LF

	   This	command	is extremely useful if the frontend does not know (or
	   does	not care to know) what files are currently on the branch, and
	   therefore cannot generate the proper	filedelete commands to update
	   the content.

	   Issuing a filedeleteall followed by the needed filemodify commands
	   to set the correct content will produce the same results as sending
	   only	the needed filemodify and filedelete commands. The
	   filedeleteall approach may however require fast-import to use
	   slightly more memory	per active branch (less	than 1 MiB for even
	   most	large projects); so frontends that can easily obtain only the
	   affected paths for a	commit are encouraged to do so.

       notemodify
	   Included in a commit	<notes_ref> command to add a new note
	   annotating a	<commit-ish> or	change this annotation contents.
	   Internally it is similar to filemodify 100644 on <commit-ish> path
	   (maybe split	into subdirectories). It's not advised to use any
	   other commands to write to the <notes_ref> tree except
	   filedeleteall to delete all existing	notes in this tree. This
	   command has two different means of specifying the content of	the
	   note.

	   External data format
	       The data	content	for the	note was already supplied by a prior
	       blob command. The frontend just needs to	connect	it to the
	       commit that is to be annotated.

			   'N' SP <dataref> SP <commit-ish> LF

	       Here <dataref> can be either a mark reference (:<idnum>)	set by
	       a prior blob command, or	a full 40-byte SHA-1 of	an existing
	       Git blob	object.

	   Inline data format
	       The data	content	for the	note has not been supplied yet.	The
	       frontend	wants to supply	it as part of this modify command.

			   'N' SP 'inline' SP <commit-ish> LF
			   data

	       See below for a detailed	description of the data	command.

	   In both formats <commit-ish>	is any of the commit specification
	   expressions also accepted by	from (see above).

   mark
       Arranges	for fast-import	to save	a reference to the current object,
       allowing	the frontend to	recall this object at a	future point in	time,
       without knowing its SHA-1. Here the current object is the object
       creation	command	the mark command appears within. This can be commit,
       tag, and	blob, but commit is the	most common usage.

		   'mark' SP ':' <idnum> LF

       where <idnum> is	the number assigned by the frontend to this mark. The
       value of	<idnum>	is expressed as	an ASCII decimal integer. The value 0
       is reserved and cannot be used as a mark. Only values greater than or
       equal to	1 may be used as marks.

       New marks are created automatically. Existing marks can be moved	to
       another object simply by	reusing	the same <idnum> in another mark
       command.

   tag
       Creates an annotated tag	referring to a specific	commit.	To create
       lightweight (non-annotated) tags	see the	reset command below.

		   'tag' SP <name> LF
		   'from' SP <commit-ish> LF
		   'tagger' (SP	<name>)? SP LT <email> GT SP <when> LF
		   data

       where <name> is the name	of the tag to create.

       Tag names are automatically prefixed with refs/tags/ when stored	in
       Git, so importing the CVS branch	symbol RELENG-1_0-FINAL	would use just
       RELENG-1_0-FINAL	for <name>, and	fast-import will write the
       corresponding ref as refs/tags/RELENG-1_0-FINAL.

       The value of <name> must	be a valid refname in Git and therefore	may
       contain forward slashes.	As LF is not valid in a	Git refname, no
       quoting or escaping syntax is supported here.

       The from	command	is the same as in the commit command; see above	for
       details.

       The tagger command uses the same	format as committer within commit;
       again see above for details.

       The data	command	following tagger must supply the annotated tag message
       (see below for data command syntax). To import an empty tag message use
       a 0 length data.	Tag 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.

       Signing annotated tags during import from within	fast-import is not
       supported. Trying to include your own PGP/GPG signature is not
       recommended, as the frontend does not (easily) have access to the
       complete	set of bytes which normally goes into such a signature.	If
       signing is required, create lightweight tags from within	fast-import
       with reset, then	create the annotated versions of those tags offline
       with the	standard git tag process.

   reset
       Creates (or recreates) the named	branch,	optionally starting from a
       specific	revision. The reset command allows a frontend to issue a new
       from command for	an existing branch, or to create a new branch from an
       existing	commit without creating	a new commit.

		   'reset' SP <ref> LF
		   ('from' SP <commit-ish> LF)?
		   LF?

       For a detailed description of <ref> and <commit-ish> see	above under
       commit and from.

       The LF after the	command	is optional (it	used to	be required).

       The reset command can also be used to create lightweight
       (non-annotated) tags. For example:

	   reset refs/tags/938
	   from	:938

       would create the	lightweight tag	refs/tags/938 referring	to whatever
       commit mark :938	references.

   blob
       Requests	writing	one file revision to the packfile. The revision	is not
       connected to any	commit;	this connection	must be	formed in a subsequent
       commit command by referencing the blob through an assigned mark.

		   'blob' LF
		   mark?
		   data

       The mark	command	is optional here as some frontends have	chosen to
       generate	the Git	SHA-1 for the blob on their own, and feed that
       directly	to commit. This	is typically more work than it's worth
       however,	as marks are inexpensive to store and easy to use.

   data
       Supplies	raw data (for use as blob/file content,	commit messages, or
       annotated tag messages) to fast-import. Data can	be supplied using an
       exact byte count	or delimited with a terminating	line. Real frontends
       intended	for production-quality conversions should always use the exact
       byte count format, as it	is more	robust and performs better. The
       delimited format	is intended primarily for testing fast-import.

       Comment lines appearing within the <raw>	part of	data commands are
       always taken to be part of the body of the data and are therefore never
       ignored by fast-import. This makes it safe to import any	file/message
       content whose lines might start with #.

       Exact byte count	format
	   The frontend	must specify the number	of bytes of data.

		       'data' SP <count> LF
		       <raw> LF?

	   where <count> is the	exact number of	bytes appearing	within <raw>.
	   The value of	<count>	is expressed as	an ASCII decimal integer. The
	   LF on either	side of	<raw> is not included in <count> and will not
	   be included in the imported data.

	   The LF after	<raw> is optional (it used to be required) but
	   recommended.	Always including it makes debugging a fast-import
	   stream easier as the	next command always starts in column 0 of the
	   next	line, even if <raw> did	not end	with an	LF.

       Delimited format
	   A delimiter string is used to mark the end of the data. fast-import
	   will	compute	the length by searching	for the	delimiter. This	format
	   is primarily	useful for testing and is not recommended for real
	   data.

		       'data' SP '<<' <delim> LF
		       <raw> LF
		       <delim> LF
		       LF?

	   where <delim> is the	chosen delimiter string. The string <delim>
	   must	not appear on a	line by	itself within <raw>, as	otherwise
	   fast-import will think the data ends	earlier	than it	really does.
	   The LF immediately trailing <raw> is	part of	<raw>. This is one of
	   the limitations of the delimited format, it is impossible to	supply
	   a data chunk	which does not have an LF as its last byte.

	   The LF after	<delim>	LF is optional (it used	to be required).

   checkpoint
       Forces fast-import to close the current packfile, start a new one, and
       to save out all current branch refs, tags and marks.

		   'checkpoint'	LF
		   LF?

       Note that fast-import automatically switches packfiles when the current
       packfile	reaches	--max-pack-size, or 4 GiB, whichever limit is smaller.
       During an automatic packfile switch fast-import does not	update the
       branch refs, tags or marks.

       As a checkpoint can require a significant amount	of CPU time and	disk
       IO (to compute the overall pack SHA-1 checksum, generate	the
       corresponding index file, and update the	refs) it can easily take
       several minutes for a single checkpoint command to complete.

       Frontends may choose to issue checkpoints during	extremely large	and
       long running imports, or	when they need to allow	another	Git process
       access to a branch. However given that a	30 GiB Subversion repository
       can be loaded into Git through fast-import in about 3 hours, explicit
       checkpointing may not be	necessary.

       The LF after the	command	is optional (it	used to	be required).

   progress
       Causes fast-import to print the entire progress line unmodified to its
       standard	output channel (file descriptor	1) when	the command is
       processed from the input	stream.	The command otherwise has no impact on
       the current import, or on any of	fast-import's internal state.

		   'progress' SP <any> LF
		   LF?

       The <any> part of the command may contain any sequence of bytes that
       does not	contain	LF. The	LF after the command is	optional. Callers may
       wish to process the output through a tool such as sed to	remove the
       leading part of the line, for example:

	   frontend | git fast-import |	sed 's/^progress //'

       Placing a progress command immediately after a checkpoint will inform
       the reader when the checkpoint has been completed and it	can safely
       access the refs that fast-import	updated.

   get-mark
       Causes fast-import to print the SHA-1 corresponding to a	mark to	stdout
       or to the file descriptor previously arranged with the --cat-blob-fd
       argument. The command otherwise has no impact on	the current import;
       its purpose is to retrieve SHA-1s that later commits might want to
       refer to	in their commit	messages.

		   'get-mark' SP ':' <idnum> LF

       This command can	be used	anywhere in the	stream that comments are
       accepted. In particular,	the get-mark command can be used in the	middle
       of a commit but not in the middle of a data command.

       See "Responses To Commands" below for details about how to read this
       output safely.

   cat-blob
       Causes fast-import to print a blob to a file descriptor previously
       arranged	with the --cat-blob-fd argument. The command otherwise has no
       impact on the current import; its main purpose is to retrieve blobs
       that may	be in fast-import's memory but not accessible from the target
       repository.

		   'cat-blob' SP <dataref> LF

       The <dataref> can be either a mark reference (:<idnum>) set previously
       or a full 40-byte SHA-1 of a Git	blob, preexisting or ready to be
       written.

       Output uses the same format as git cat-file --batch:

	   <sha1> SP 'blob' SP <size> LF
	   <contents> LF

       This command can	be used	anywhere in the	stream that comments are
       accepted. In particular,	the cat-blob command can be used in the	middle
       of a commit but not in the middle of a data command.

       See "Responses To Commands" below for details about how to read this
       output safely.

   ls
       Prints information about	the object at a	path to	a file descriptor
       previously arranged with	the --cat-blob-fd argument. This allows
       printing	a blob from the	active commit (with cat-blob) or copying a
       blob or tree from a previous commit for use in the current one (with
       filemodify).

       The ls command can be used anywhere in the stream that comments are
       accepted, including the middle of a commit.

       Reading from the	active commit
	   This	form can only be used in the middle of a commit. The path
	   names a directory entry within fast-import's	active commit. The
	   path	must be	quoted in this case.

		       'ls' SP <path> LF

       Reading from a named tree
	   The <dataref> can be	a mark reference (:<idnum>) or the full
	   40-byte SHA-1 of a Git tag, commit, or tree object, preexisting or
	   waiting to be written. The path is relative to the top level	of the
	   tree	named by <dataref>.

		       'ls' SP <dataref> SP <path> LF

       See filemodify above for	a detailed description of <path>.

       Output uses the same format as git ls-tree <tree> -- <path>:

	   <mode> SP ('blob' | 'tree' |	'commit') SP <dataref> HT <path> LF

       The <dataref> represents	the blob, tree,	or commit object at <path> and
       can be used in later get-mark, cat-blob,	filemodify, or ls commands.

       If there	is no file or subtree at that path, git	fast-import will
       instead report

	   missing SP <path> LF

       See "Responses To Commands" below for details about how to read this
       output safely.

   feature
       Require that fast-import	supports the specified feature,	or abort if it
       does not.

		   'feature' SP	<feature> ('=' <argument>)? LF

       The <feature> part of the command may be	any one	of the following:

       date-format, export-marks, relative-marks, no-relative-marks, force
	   Act as though the corresponding command-line	option with a leading
	   -- was passed on the	command	line (see OPTIONS, above).

       import-marks, import-marks-if-exists
	   Like	--import-marks except in two respects: first, only one
	   "feature import-marks" or "feature import-marks-if-exists" command
	   is allowed per stream; second, an --import-marks= or
	   --import-marks-if-exists command-line option	overrides any of these
	   "feature" commands in the stream; third, "feature
	   import-marks-if-exists" like	a corresponding	command-line option
	   silently skips a nonexistent	file.

       get-mark, cat-blob, ls
	   Require that	the backend support the	get-mark, cat-blob, or ls
	   command respectively. Versions of fast-import not supporting	the
	   specified command will exit with a message indicating so. This lets
	   the import error out	early with a clear message, rather than
	   wasting time	on the early part of an	import before the unsupported
	   command is detected.

       notes
	   Require that	the backend support the	notemodify (N) subcommand to
	   the commit command. Versions	of fast-import not supporting notes
	   will	exit with a message indicating so.

       done
	   Error out if	the stream ends	without	a done command.	Without	this
	   feature, errors causing the frontend	to end abruptly	at a
	   convenient point in the stream can go undetected. This may occur,
	   for example,	if an import front end dies in mid-operation without
	   emitting SIGTERM or SIGKILL at its subordinate git fast-import
	   instance.

   option
       Processes the specified option so that git fast-import behaves in a way
       that suits the frontend's needs.	Note that options specified by the
       frontend	are overridden by any options the user may specify to git
       fast-import itself.

	       'option'	SP <option> LF

       The <option> part of the	command	may contain any	of the options listed
       in the OPTIONS section that do not change import	semantics, without the
       leading -- and is treated in the	same way.

       Option commands must be the first commands on the input (not counting
       feature commands), to give an option command after any non-option
       command is an error.

       The following command-line options change import	semantics and may
       therefore not be	passed as option:

       o   date-format

       o   import-marks

       o   export-marks

       o   cat-blob-fd

       o   force

   done
       If the done feature is not in use, treated as if	EOF was	read. This can
       be used to tell fast-import to finish early.

       If the --done command-line option or feature done command is in use,
       the done	command	is mandatory and marks the end of the stream.

RESPONSES TO COMMANDS
       New objects written by fast-import are not available immediately. Most
       fast-import commands have no visible effect until the next checkpoint
       (or completion).	The frontend can send commands to fill fast-import's
       input pipe without worrying about how quickly they will take effect,
       which improves performance by simplifying scheduling.

       For some	frontends, though, it is useful	to be able to read back	data
       from the	current	repository as it is being updated (for example when
       the source material describes objects in	terms of patches to be applied
       to previously imported objects).	This can be accomplished by connecting
       the frontend and	fast-import via	bidirectional pipes:

	   mkfifo fast-import-output
	   frontend <fast-import-output	|
	   git fast-import >fast-import-output

       A frontend set up this way can use progress, get-mark, ls, and cat-blob
       commands	to read	information from the import in progress.

       To avoid	deadlock, such frontends must completely consume any pending
       output from progress, ls, get-mark, and cat-blob	before performing
       writes to fast-import that might	block.

CRASH REPORTS
       If fast-import is supplied invalid input	it will	terminate with a
       non-zero	exit status and	create a crash report in the top level of the
       Git repository it was importing into. Crash reports contain a snapshot
       of the internal fast-import state as well as the	most recent commands
       that lead up to the crash.

       All recent commands (including stream comments, file changes and
       progress	commands) are shown in the command history within the crash
       report, but raw file data and commit messages are excluded from the
       crash report. This exclusion saves space	within the report file and
       reduces the amount of buffering that fast-import	must perform during
       execution.

       After writing a crash report fast-import	will close the current
       packfile	and export the marks table. This allows	the frontend developer
       to inspect the repository state and resume the import from the point
       where it	crashed. The modified branches and tags	are not	updated	during
       a crash,	as the import did not complete successfully. Branch and	tag
       information can be found	in the crash report and	must be	applied
       manually	if the update is needed.

       An example crash:

	   $ cat >in <<END_OF_INPUT
	   # my	very first test	commit
	   commit refs/heads/master
	   committer Shawn O. Pearce <spearce> 19283 -0400
	   # who is that guy anyway?
	   data	<<EOF
	   this	is my commit
	   EOF
	   M 644 inline	.gitignore
	   data	<<EOF
	   .gitignore
	   EOF
	   M 777 inline	bob
	   END_OF_INPUT

	   $ git fast-import <in
	   fatal: Corrupt mode:	M 777 inline bob
	   fast-import:	dumping	crash report to	.git/fast_import_crash_8434

	   $ cat .git/fast_import_crash_8434
	   fast-import crash report:
	       fast-import process: 8434
	       parent process	  : 1391
	       at Sat Sep 1 00:58:12 2007

	   fatal: Corrupt mode:	M 777 inline bob

	   Most	Recent Commands	Before Crash
	   ---------------------------------
	     # my very first test commit
	     commit refs/heads/master
	     committer Shawn O.	Pearce <spearce> 19283 -0400
	     # who is that guy anyway?
	     data <<EOF
	     M 644 inline .gitignore
	     data <<EOF
	   * M 777 inline bob

	   Active Branch LRU
	   -----------------
	       active_branches = 1 cur,	5 max

	   pos	clock name
	   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	    1)	    0 refs/heads/master

	   Inactive Branches
	   -----------------
	   refs/heads/master:
	     status	 : active loaded dirty
	     tip commit	 : 0000000000000000000000000000000000000000
	     old tree	 : 0000000000000000000000000000000000000000
	     cur tree	 : 0000000000000000000000000000000000000000
	     commit clock: 0
	     last pack	 :

	   -------------------
	   END OF CRASH	REPORT

TIPS AND TRICKS
       The following tips and tricks have been collected from various users of
       fast-import, and	are offered here as suggestions.

   Use One Mark	Per Commit
       When doing a repository conversion, use a unique	mark per commit	(mark
       :<n>) and supply	the --export-marks option on the command line.
       fast-import will	dump a file which lists	every mark and the Git object
       SHA-1 that corresponds to it. If	the frontend can tie the marks back to
       the source repository, it is easy to verify the accuracy	and
       completeness of the import by comparing each Git	commit to the
       corresponding source revision.

       Coming from a system such as Perforce or	Subversion this	should be
       quite simple, as	the fast-import	mark can also be the Perforce
       changeset number	or the Subversion revision number.

   Freely Skip Around Branches
       Don't bother trying to optimize the frontend to stick to	one branch at
       a time during an	import.	Although doing so might	be slightly faster for
       fast-import, it tends to	increase the complexity	of the frontend	code
       considerably.

       The branch LRU builtin to fast-import tends to behave very well,	and
       the cost	of activating an inactive branch is so low that	bouncing
       around between branches has virtually no	impact on import performance.

   Handling Renames
       When importing a	renamed	file or	directory, simply delete the old
       name(s) and modify the new name(s) during the corresponding commit. Git
       performs	rename detection after-the-fact, rather	than explicitly	during
       a commit.

   Use Tag Fixup Branches
       Some other SCM systems let the user create a tag	from multiple files
       which are not from the same commit/changeset. Or	to create tags which
       are a subset of the files available in the repository.

       Importing these tags as-is in Git is impossible without making at least
       one commit which	"fixes up" the files to	match the content of the tag.
       Use fast-import's reset command to reset	a dummy	branch outside of your
       normal branch space to the base commit for the tag, then	commit one or
       more file fixup commits,	and finally tag	the dummy branch.

       For example since all normal branches are stored	under refs/heads/ name
       the tag fixup branch TAG_FIXUP. This way	it is impossible for the fixup
       branch used by the importer to have namespace conflicts with real
       branches	imported from the source (the name TAG_FIXUP is	not
       refs/heads/TAG_FIXUP).

       When committing fixups, consider	using merge to connect the commit(s)
       which are supplying file	revisions to the fixup branch. Doing so	will
       allow tools such	as git blame to	track through the real commit history
       and properly annotate the source	files.

       After fast-import terminates the	frontend will need to do rm
       .git/TAG_FIXUP to remove	the dummy branch.

   Import Now, Repack Later
       As soon as fast-import completes	the Git	repository is completely valid
       and ready for use. Typically this takes only a very short time, even
       for considerably	large projects (100,000+ commits).

       However repacking the repository	is necessary to	improve	data locality
       and access performance. It can also take	hours on extremely large
       projects	(especially if -f and a	large --window parameter is used).
       Since repacking is safe to run alongside	readers	and writers, run the
       repack in the background	and let	it finish when it finishes. There is
       no reason to wait to explore your new Git project!

       If you choose to	wait for the repack, don't try to run benchmarks or
       performance tests until repacking is completed. fast-import outputs
       suboptimal packfiles that are simply never seen in real use situations.

   Repacking Historical	Data
       If you are repacking very old imported data (e.g. older than the	last
       year), consider expending some extra CPU	time and supplying --window=50
       (or higher) when	you run	git repack. This will take longer, but will
       also produce a smaller packfile.	You only need to expend	the effort
       once, and everyone using	your project will benefit from the smaller
       repository.

   Include Some	Progress Messages
       Every once in a while have your frontend	emit a progress	message	to
       fast-import. The	contents of the	messages are entirely free-form, so
       one suggestion would be to output the current month and year each time
       the current commit date moves into the next month. Your users will feel
       better knowing how much of the data stream has been processed.

PACKFILE OPTIMIZATION
       When packing a blob fast-import always attempts to deltify against the
       last blob written. Unless specifically arranged for by the frontend,
       this will probably not be a prior version of the	same file, so the
       generated delta will not	be the smallest	possible. The resulting
       packfile	will be	compressed, but	will not be optimal.

       Frontends which have efficient access to	all revisions of a single file
       (for example reading an RCS/CVS ,v file)	can choose to supply all
       revisions of that file as a sequence of consecutive blob	commands. This
       allows fast-import to deltify the different file	revisions against each
       other, saving space in the final	packfile. Marks	can be used to later
       identify	individual file	revisions during a sequence of commit
       commands.

       The packfile(s) created by fast-import do not encourage good disk
       access patterns.	This is	caused by fast-import writing the data in the
       order it	is received on standard	input, while Git typically organizes
       data within packfiles to	make the most recent (current tip) data	appear
       before historical data. Git also	clusters commits together, speeding up
       revision	traversal through better cache locality.

       For this	reason it is strongly recommended that users repack the
       repository with git repack -a -d	after fast-import completes, allowing
       Git to reorganize the packfiles for faster data access. If blob deltas
       are suboptimal (see above) then also adding the -f option to force
       recomputation of	all deltas can significantly reduce the	final packfile
       size (30-50% smaller can	be quite typical).

MEMORY UTILIZATION
       There are a number of factors which affect how much memory fast-import
       requires	to perform an import. Like critical sections of	core Git,
       fast-import uses	its own	memory allocators to amortize any overheads
       associated with malloc. In practice fast-import tends to	amortize any
       malloc overheads	to 0, due to its use of	large block allocations.

   per object
       fast-import maintains an	in-memory structure for	every object written
       in this execution. On a 32 bit system the structure is 32 bytes,	on a
       64 bit system the structure is 40 bytes (due to the larger pointer
       sizes). Objects in the table are	not deallocated	until fast-import
       terminates. Importing 2 million objects on a 32 bit system will require
       approximately 64	MiB of memory.

       The object table	is actually a hashtable	keyed on the object name (the
       unique SHA-1). This storage configuration allows	fast-import to reuse
       an existing or already written object and avoid writing duplicates to
       the output packfile. Duplicate blobs are	surprisingly common in an
       import, typically due to	branch merges in the source.

   per mark
       Marks are stored	in a sparse array, using 1 pointer (4 bytes or 8
       bytes, depending	on pointer size) per mark. Although the	array is
       sparse, frontends are still strongly encouraged to use marks between 1
       and n, where n is the total number of marks required for	this import.

   per branch
       Branches	are classified as active and inactive. The memory usage	of the
       two classes is significantly different.

       Inactive	branches are stored in a structure which uses 96 or 120	bytes
       (32 bit or 64 bit systems, respectively), plus the length of the	branch
       name (typically under 200 bytes), per branch. fast-import will easily
       handle as many as 10,000	inactive branches in under 2 MiB of memory.

       Active branches have the	same overhead as inactive branches, but	also
       contain copies of every tree that has been recently modified on that
       branch. If subtree include has not been modified	since the branch
       became active, its contents will	not be loaded into memory, but if
       subtree src has been modified by	a commit since the branch became
       active, then its	contents will be loaded	in memory.

       As active branches store	metadata about the files contained on that
       branch, their in-memory storage size can	grow to	a considerable size
       (see below).

       fast-import automatically moves active branches to inactive status
       based on	a simple least-recently-used algorithm.	The LRU	chain is
       updated on each commit command. The maximum number of active branches
       can be increased	or decreased on	the command line with
       --active-branches=.

   per active tree
       Trees (aka directories) use just	12 bytes of memory on top of the
       memory required for their entries (see "per active file"	below).	The
       cost of a tree is virtually 0, as its overhead amortizes	out over the
       individual file entries.

   per active file entry
       Files (and pointers to subtrees)	within active trees require 52 or 64
       bytes (32/64 bit	platforms) per entry. To conserve space, file and tree
       names are pooled	in a common string table, allowing the filename
       "Makefile" to use just 16 bytes (after including	the string header
       overhead) no matter how many times it occurs within the project.

       The active branch LRU, when coupled with	the filename string pool and
       lazy loading of subtrees, allows	fast-import to efficiently import
       projects	with 2,000+ branches and 45,114+ files in a very limited
       memory footprint	(less than 2.7 MiB per active branch).

SIGNALS
       Sending SIGUSR1 to the git fast-import process ends the current
       packfile	early, simulating a checkpoint command.	The impatient operator
       can use this facility to	peek at	the objects and	refs from an import in
       progress, at the	cost of	some added running time	and worse compression.

SEE ALSO
       git-fast-export(1)

GIT
       Part of the git(1) suite

Git 2.13.2			  06/24/2017		    GIT-FAST-IMPORT(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | PERFORMANCE | DEVELOPMENT COST | PARALLEL OPERATION | TECHNICAL DISCUSSION | INPUT FORMAT | RESPONSES TO COMMANDS | CRASH REPORTS | TIPS AND TRICKS | PACKFILE OPTIMIZATION | MEMORY UTILIZATION | SIGNALS | SEE ALSO | GIT

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