From d333998e259ac1976c4d56e8b607e59cb755f700 Mon Sep 17 00:00:00 2001 From: Junio C Hamano Date: Fri, 9 Feb 2007 08:38:48 +0000 Subject: [PATCH] Autogenerated HTML docs for v1.5.0-rc4-16-g9e258 --- git-am.html | 11 ++- git-am.txt | 4 + git-fast-import.html | 169 ++++++++++++++++++++++--------------------- git-fast-import.txt | 169 ++++++++++++++++++++++--------------------- git-log.html | 4 +- git-log.txt | 2 +- git-pull.html | 59 ++++++++++++++- git-pull.txt | 54 ++++++++++++++ git-rebase.html | 15 +++- git-rebase.txt | 8 +- git-reflog.html | 16 +++- git-reflog.txt | 17 ++++- git-show.html | 4 +- git-show.txt | 3 + git.html | 2 +- 15 files changed, 351 insertions(+), 186 deletions(-) diff --git a/git-am.html b/git-am.html index 2a3c89415..f8badfb2c 100644 --- a/git-am.html +++ b/git-am.html @@ -374,6 +374,15 @@ default. You could use --no-utf8 to override this.

+-C<n> +
+
+

+ This flag is passed to the git-apply program that applies + the patch. +

+
+
--interactive
@@ -440,7 +449,7 @@ names.

diff --git a/git-am.txt b/git-am.txt index aa4ce1ddb..f7d551e2c 100644 --- a/git-am.txt +++ b/git-am.txt @@ -64,6 +64,10 @@ default. You could use `--no-utf8` to override this. This flag is passed to the `git-apply` program that applies the patch. +-C:: + This flag is passed to the `git-apply` program that applies + the patch. + --interactive:: Run interactively, just like git-applymbox. diff --git a/git-fast-import.html b/git-fast-import.html index 2c08b43b6..61b066825 100644 --- a/git-fast-import.html +++ b/git-fast-import.html @@ -279,13 +279,13 @@ git-fast-import(1) Manual Page

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 (gfi).

-

gfi reads a mixed command/data stream from standard input and +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 gfi backend itself can import into an empty repository (one that +

The fast-import backend itself can import into an empty repository (one that has already been initialized by git-init(1)) or incrementally update an existing populated repository. Whether or not incremental imports are supported from a particular foreign source depends on @@ -300,7 +300,7 @@ the frontend program in use.

Specify the type of dates the frontend will supply to - gfi within author, committer and tagger commands. + fast-import within author, committer and tagger commands. See “Date Formats” below for details about which formats are supported, and their syntax.

@@ -361,7 +361,7 @@ the frontend program in use.

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

@@ -371,9 +371,9 @@ the frontend program in use.

- Display some basic statistics about the objects gfi has + Display some basic statistics about the objects fast-import has created, the packfiles they were stored into, and the - memory used by gfi during this run. Showing this output + memory used by fast-import during this run. Showing this output is currently the default, but can be disabled with --quiet.

@@ -381,40 +381,40 @@ the frontend program in use.

Performance

-

The design of gfi allows it to import large projects in a minimum +

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 gfi and feed it a constant stream of data, +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 (gfi +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 gfi tends to weigh in at approximately 200 +

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 gfi, and sometimes even to Git. This is +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 gfi are safe to +

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 gfi).

-

gfi does not lock the branch or tag refs it is actively importing. -After the import, during its ref update phase, gfi tests each +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, gfi will skip updating that ref and instead -prints a warning message. gfi will always attempt to update all +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 its recommended that this only be used on an otherwise quiet repository. Using --force @@ -422,33 +422,33 @@ is not necessary for an initial import into an empty repository.

Technical Discussion

-

gfi tracks a set of branches in memory. Any branch can be created +

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.

-

gfi does not use or alter the current working directory, or any +

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 gfi to run very quickly, as it does not +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 gfi input format is text (ASCII) based. This text based +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.

-

gfi is very strict about its input. Where we say SP below we mean +

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. 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 gfi when it encounters +spaces in their name, or early termination of fast-import when it encounters unexpected input.

Date Formats

The following date formats are supported. A frontend should select @@ -461,7 +461,7 @@ in the --date-format=<fmt> command line option.

This is the Git native format and is <time> SP <offutc>. - It is also gfi's default format, if --date-format was + 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 @@ -476,9 +476,9 @@ advisement to help formatting routines display the timestamp.

“+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 the offset from UTC can be easily assumed.

+case a reasonable offset from UTC could be assumed.

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

+variation in formatting will cause fast-import to reject the value.

rfc2822 @@ -488,7 +488,7 @@ variation in formatting will cause gfi to reject the value.

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. Its the +parser is accurate, but a little on the lenient side. It is the same parser used by git-am(1) when applying patches received from email.

Some malformed strings may be accepted as valid dates. In some of @@ -500,13 +500,14 @@ Seriously malformed strings will be rejected.

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 is formatted in RFC 2822 style dates, -the frontend should let gfi handle the parsing and conversion +

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 -is already in UNIX-epoch format, or is easily convertible to -that format, as there is no ambiguity in parsing.

+already uses UNIX-epoch format, can be coaxed to give dates in that +format, or its format is easiliy convertible to it, as there is no +ambiguity in parsing.

now @@ -518,7 +519,7 @@ that format, as there is no ambiguity in parsing.

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 gfi. There is no way to specify a different time or +created by fast-import. There is no way to specify a different time or timezone.

This particular format is supplied as its short to implement and may be useful to a process that wants to create a new commit @@ -533,7 +534,7 @@ date format other than now.

Commands

-

gfi accepts several commands to update the current repository +

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.

@@ -583,7 +584,7 @@ and control the current import process. More detailed discussion

- Forces gfi to close the current packfile, generate its + 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. @@ -611,7 +612,7 @@ 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 gfi to save a +

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 @@ -620,7 +621,7 @@ from any imported 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 gfi does not permit other encodings to be specified.

+UTF-8, as fast-import does not permit other encodings to be specified.

Zero or more filemodify, filedelete and filedeleteall commands may be included to update the contents of the branch prior to creating the commit. These commands may be supplied in any order. @@ -630,7 +631,7 @@ wipes the branch clean (see below).

author

An author command may optionally appear, if the author information might differ from the committer information. If author is omitted -then gfi will automatically use the committer's information for +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

@@ -649,11 +650,11 @@ See “Date Formats” above for the set of supported formats, and their syntax.

from

Only valid for the first commit made on this branch by this -gfi process. The from command is used to specify the commit +fast-import process. 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.

Omitting the from command in the first commit of a new branch will -cause gfi to create that commit with no ancestor. This tends to be +cause fast-import to create that commit with no ancestor. This tends to be desired only for the initial commit of a project. Omitting the from command on existing branches is required, as the current commit on that branch is automatically assumed to be the first @@ -664,8 +665,8 @@ quoting or escaping syntax is supported within <committish>.

  • -The name of an existing branch already in gfi's internal branch - table. If gfi doesn't know the name, its treated as a SHA-1 +The name of an existing branch already in fast-import's internal branch + table. If fast-import doesn't know the name, its treated as a SHA-1 expression.

    • @@ -673,7 +674,7 @@ The name of an existing branch already in gfi's internal branch

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

    -

    The reason gfi uses : to denote a mark reference is this character +

    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 distingush between the mark 42 (:42) and the branch 42 (42 or refs/heads/42), or an abbreviated SHA-1 which happened to @@ -698,16 +699,16 @@ current branch value should be written as:

            from refs/heads/branch^0
-

The ^0 suffix is necessary as gfi does not permit a branch to +

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 -gfi to resolve the commit through Git's revision parsing library, +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, and makes the current commit a merge commit. An unlimited number of merge commands per -commit are permitted by gfi, thereby establishing an n-way merge. +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 merge @@ -832,12 +833,12 @@ 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 gfi to use slightly +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.

mark

-

Arranges for gfi to save a reference to the current object, allowing +

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, @@ -867,7 +868,7 @@ lightweight (non-annotated) tags see the reset command below.

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 gfi will write the +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, @@ -880,12 +881,12 @@ above for details.

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 gfi does not permit other encodings to be specified.

-

Signing annotated tags during import from within gfi is not +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 gfi with +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(1) process.

reset

@@ -930,11 +931,11 @@ directly to commit. This is typically more work than its 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 gfi. Data can be supplied using an exact +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 gfi.

+The delimited format is intended primarily for testing fast-import.

Exact byte count format @@ -959,7 +960,7 @@ Delimited format

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

@@ -971,23 +972,23 @@ Delimited format

where <delim> is the chosen delimiter string. The string <delim> must not appear on a line by itself within <raw>, as otherwise -gfi will think the data ends earlier than it really does. The LF +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.

checkpoint

-

Forces gfi to close the current packfile, start a new one, and to +

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 gfi automatically switches packfiles when the current +

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 gfi does not update +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 @@ -996,30 +997,30 @@ 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 gfi in about 3 hours, +repository can be loaded into Git through fast-import in about 3 hours, explicit checkpointing may not be necessary.

Tips and Tricks

The following tips and tricks have been collected from various -users of gfi, and are offered here as suggestions.

+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. gfi will dump a file which lists every mark and the Git +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 gfi mark can also be the Perforce changeset +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 gfi, it tends to increase the complexity of the frontend +faster for fast-import, it tends to increase the complexity of the frontend code considerably.

-

The branch LRU builtin to gfi tends to behave very well, and the +

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.

Use Tag Fixup Branches

@@ -1028,7 +1029,7 @@ 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 gfi's reset command to reset a dummy branch +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.

@@ -1042,10 +1043,10 @@ commit(s) which are supplying file revisions to the fixup branch. Doing so will allow tools such as git-blame(1) to track through the real commit history and properly annotate the source files.

-

After gfi terminates the frontend will need to do rm .git/TAG_FIXUP +

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 gfi completes the Git repository is completely valid +

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

However repacking the repository is necessary to improve data @@ -1055,7 +1056,7 @@ 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. gfi outputs +or performance tests until repacking is completed. fast-import outputs suboptimal packfiles that are simply never seen in real use situations.

Repacking Historical Data

@@ -1068,7 +1069,7 @@ project will benefit from the smaller repository.

Packfile Optimization

-

When packing a blob gfi always attempts to deltify against the last +

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 @@ -1076,18 +1077,18 @@ 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 gfi to deltify the different file +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 gfi do not encourage good disk access -patterns. This is caused by gfi writing the data in the order +

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 gfi completes, allowing +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 @@ -1095,20 +1096,20 @@ final packfile size (30-50% smaller can be quite typical).

Memory Utilization

-

There are a number of factors which affect how much memory gfi +

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

per object

-

gfi maintains an in-memory structure for every object written in +

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 -gfi terminates. Importing 2 million objects on a 32 bit system +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 gfi to reuse +(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.

@@ -1123,7 +1124,7 @@ this import.

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. gfi will +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 @@ -1135,7 +1136,7 @@ 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).

-

gfi automatically moves active branches to inactive status based on +

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=.

@@ -1151,7 +1152,7 @@ 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 gfi to efficiently import +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).

@@ -1169,7 +1170,7 @@ memory footprint (less than 2.7 MiB per active branch).

diff --git a/git-fast-import.txt b/git-fast-import.txt index 0b64d3348..2a5052072 100644 --- a/git-fast-import.txt +++ b/git-fast-import.txt @@ -15,15 +15,15 @@ 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 (gfi). +stored there to git-fast-import. -gfi reads a mixed command/data stream from standard input and +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 gfi backend itself can import into an empty repository (one that +The fast-import backend itself can import into an empty repository (one that has already been initialized by gitlink:git-init[1]) or incrementally update an existing populated repository. Whether or not incremental imports are supported from a particular foreign source depends on @@ -34,7 +34,7 @@ OPTIONS ------- --date-format=:: Specify the type of dates the frontend will supply to - gfi within `author`, `committer` and `tagger` commands. + fast-import within `author`, `committer` and `tagger` commands. See ``Date Formats'' below for details about which formats are supported, and their syntax. @@ -65,28 +65,28 @@ OPTIONS have been completed. --quiet:: - Disable all non-fatal output, making gfi silent when it + 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 gfi has + Display some basic statistics about the objects fast-import has created, the packfiles they were stored into, and the - memory used by gfi during this run. Showing this output + memory used by fast-import during this run. Showing this output is currently the default, but can be disabled with \--quiet. Performance ----------- -The design of gfi allows it to import large projects in a minimum +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 gfi and feed it a constant stream of data, +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 (gfi +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). @@ -94,28 +94,28 @@ destination Git repository (due to less IO contention). Development Cost ---------------- -A typical frontend for gfi tends to weigh in at approximately 200 +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 gfi, and sometimes even to Git. This is +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 gfi are safe to +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 gfi). +are never used by fast-import). -gfi does not lock the branch or tag refs it is actively importing. -After the import, during its ref update phase, gfi tests each +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, gfi will skip updating that ref and instead -prints a warning message. gfi will always attempt to update all +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 its recommended that @@ -125,35 +125,35 @@ is not necessary for an initial import into an empty repository. Technical Discussion -------------------- -gfi tracks a set of branches in memory. Any branch can be created +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. -gfi does not use or alter the current working directory, or any +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 gfi to run very quickly, as it does not +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 gfi input format is text (ASCII) based. This text based +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. -gfi is very strict about its input. Where we say SP below we mean +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. 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 gfi when it encounters +spaces in their name, or early termination of fast-import when it encounters unexpected input. Date Formats @@ -164,7 +164,7 @@ in the \--date-format= command line option. `raw`:: This is the Git native format and is `