Git::Repository(3)

NAME
Git::Repository - Perl interface to Git repositories

SYNOPSIS
    use Git::Repository;

    # start from an existing repository
    $r = Git::Repository->new( git_dir => $gitdir );

    # start from an existing working copy
    $r = Git::Repository->new( work_tree => $dir );

    # or init our own repository first
    Git::Repository->run( init => $dir, ... );
    $r = Git::Repository->new( work_tree => $dir );

    # or clone from a URL first
    Git::Repository->run( clone => $url, $dir, ... );
    $r = Git::Repository->new( work_tree => $dir );

    # run commands
    # - get the full output (no errput)
    $output = $r->run(@cmd);

    # - get the full output as a list of lines (no errput)
    @output = $r->run(@cmd);

    # - obtain a Git::Repository::Command object
    $cmd = $r->command(@cmd);

    # obtain version information
    my $version = $r->version();

    # compare current git version
    if ( $r->version_gt('1.6.5') ) {
        ...;
    }

DESCRIPTION
"Git::Repository" is a Perl interface to Git, for scripted interactions with repositories. It's a low-level interface that allows calling any Git command, whether porcelain or plumbing, including bidirectional commands such as "git commit-tree".

A "Git::Repository" object simply provides context to the git commands being run. It is possible to call the "command()" and "run()" methods against the class itself, and the context (typically current working directory) will be obtained from the options and environment.

As a low-level interface, it provides no sugar for particular Git commands. Specifically, it will not prepare environment variables that individual Git commands may need or use.

However, the "GIT_DIR" and "GIT_WORK_TREE" environment variables are special: if the command is run in the context of a "Git::Repository" object, they will be overridden by the object's "git_dir" and "work_tree" attributes, respectively. It is however still possible to override them if necessary, using the "env" option.

"Git::Repository" requires at least Git 1.5.0, and is expected to support any later version.

See "Git::Repository::Tutorial" for more code examples.

CONSTRUCTORS
There are two ways to create "Git::Repository" objects:

  new( %args, $options )
Create a new "Git::Repository" object, based on an existing Git repository.

Parameters are:

git_dir => $gitdir
    The location of the git repository (.git directory or equivalent).

    For backward compatibility with versions 1.06 and before, "repository" is accepted in place of "git_dir" (but the newer name takes precedence).

work_tree => $dir
    The location of the git working copy (for a non-bare repository).

    If "work_tree" actually points to a subdirectory of the work tree, "Git::Repository" will automatically recompute the proper value.

    For backward compatibility with versions 1.06 and before, "working_copy" is accepted in place of "work_tree" (but the newer name takes precedence).

At least one of the two parameters is required. Usually, one is enough, as "Git::Repository" can work out where the other directory (if any) is.

"new()" also accepts a reference to an option hash which will be used as the default by "Git::Repository::Command" when working with the corresponding "Git::Repository" instance.

So this:

    my $options = {
        git => '/path/to/some/other/git',
        env => {
            GIT_COMMITTER_EMAIL => 'book@cpan.org',
            GIT_COMMITTER_NAME  => 'Philippe Bruhat (BooK)',
        },
    };
    my $r = Git::Repository->new(
        work_tree => $dir,
        $options
    );

is equivalent to explicitly passing the option hash to each "run()" or "command()".

It probably makes no sense to set the "input" option in "new()", but Git::Repository won't stop you. Note that on some systems, some git commands may close standard input on startup, which will cause a "SIGPIPE". Git::Repository::Command will raise an exception.

  create( @cmd )
The "create()" method is deprecated, and will go away in the future.

Runs a repository initialization command (like "init" or "clone") and returns a "Git::Repository" object pointing to it. @cmd may contain a hashref with options (see Git::Repository::Command.

Do not use the -q option on such commands. "create()" needs to parse their output to find the path to the repository.

"create()" also accepts a reference to an option hash which will be used to set up the returned "Git::Repository" instance.

Now that "create()" is deprecated, instead of:

    $r = Git::Repository->create( ... );

simply do it in two steps:

    Git::Repository->run( ... );
    $r = Git::Repository->new( ... );

METHODS
"Git::Repository" supports the following methods:

  command( @cmd )
Runs the git sub-command and options, and returns a "Git::Repository::Command" object pointing to the sub-process running the command.

As described in the Git::Repository::Command documentation, @cmd may also contain a hashref containing options for the command.

  run( @cmd )
Runs the command and returns the output as a string in scalar context, or as a list of lines in list context. Also accepts a hashref of options.

Lines are automatically "chomp"ed.

If the git command printed anything on stderr, it will be printed as warnings. If the git sub-process exited with status 128 (fatal error), or 129 (usage message), "run()" will "die()".

  git_dir()
Returns the repository path.

  repo_path()
For backward compatibility with versions 1.06 and before, "repo_path()" it provided as an alias to "git_dir()".

  work_tree()
Returns the working copy path. Used as current working directory by "Git::Repository::Command".

  wc_path()
For backward compatibility with versions 1.06 and before, "wc_path()" it provided as an alias to "work_tree()".

  options()
Return the option hash that was passed to "Git::Repository->new()".

  version()
Return the version of git, as given by "git --version".

  Version-comparison "operators"
Git evolves very fast, and new features are constantly added. To facilitate the creation of programs that can properly handle the wide variety of Git versions seen in the wild, a number of version comparison "operators" are available.

They are named "version_op" where op is the equivalent of the Perl operators "lt", "gt", "le", "ge", "eq", "ne". They return a boolean value, obtained by comparing the version of the git binary and the version string passed as parameter.

The methods are:

version_lt( $version )
version_gt( $version )
version_le( $version )
version_ge( $version )
version_eq( $version )
version_ne( $version )

All those methods also accept an option hash, just like the others.

Note that there are a small number of cases where the version comparison operators will not compare versions correctly for very old versions of Git. Typical example is "1.0.0a gt 1.0.0" which should return true, but doesn't. This only matters in comparisons, only for version numbers prior to "1.4.0-rc1" (June 2006), and only when the compared versions are very close.

Other issues exist when comparing development version numbers with one another. For example, 1.7.1.1 is greater than both "1.7.1.1.gc8c07" and "1.7.1.1.g5f35a", and 1.7.1 is less than both. Obviously, "1.7.1.1.gc8c07" will compare as greater than "1.7.1.1.g5f35a" (asciibetically), but in fact these two version numbers cannot be compared, as they are two siblings children of the commit tagged "v1.7.1").

If one were to compute the set of all possible version numbers (as returned by "git --version") for all git versions that can be compiled from each commit in the git.git repository, the result would not be a totally ordered set. Big deal.

Also, don't be too precise when requiring the minimum version of Git that supported a given feature. The precise commit in git.git at which a given feature was added doesn't mean as much as the release branch in which that commit was merged.

PLUGIN SUPPORT
"Git::Repository" intentionally has only few methods. The idea is to provide a lightweight wrapper around git, to be used to create interesting tools based on Git.

However, people will want to add extra functionality to "Git::Repository", the obvious example being a "log()" method that returns simple objects with useful attributes.

Taking the hypothetical "Git::Repository::Plugin::Hello" module which source code is listed in the previous reference, the methods it provides would be loaded and used as follows:

    use Git::Repository qw( Hello );

    my $r = Git::Repository->new();
    print $r->hello();
    print $r->hello_gitdir();

It's possible to load only a selection of methods from the plugin:

    use Git::Repository [ Hello => 'hello' ];

    my $r = Git::Repository->new();
    print $r->hello();

    # dies: Can't locate object method "hello_gitdir"
    print $r->hello_gitdir();

If your plugin lives in another namespace than "Git::Repository::Plugin::", just prefix the fully qualified class name with a "+". For example:

    use Git::Repository qw( +MyGit::Hello );

See Git::Repository::Plugin about how to create a new plugin.

OTHER PERL GIT WRAPPERS
A number of Perl git wrappers already exist. Why create a new one?

I have a lot of ideas of nice things to do with Git as a tool to manipulate blobs, trees, and tags, that may or may not represent revision history of a project. A lot of those commands can output huge amounts of data, which I need to be able to process in chunks. Some of these commands also expect to receive input.

What follows is a short list of "missing features" that I was looking for when I looked at the existing Git wrappers on CPAN. They are the "rational" reason for writing my own (the real reason being of course "I thought it would be fun, and I enjoyed doing it").

Even though it works well for me and others, "Git::Repository" has its own shortcomings: it is a low-level interface to Git commands, anything complex requires you to deal with input/output handles, it provides no high-level interface to generate actual Git commands or process the output of commands (but have a look at the plugins), it doesn't fully work under Win32 yet, etc. One the following modules may therefore be better suited for your needs, depending on what you're trying to achieve.

  Git.pm
Git.pm is not on CPAN. It is usually packaged with Git, and installed with the system Perl libraries. Not being on CPAN makes it harder to install in any Perl. It makes it harder for a CPAN library to depend on it.

It doesn't allow calling "git init" or "git clone".

The "command_bidi_pipe" function especially has problems: <http://kerneltrap.org/mailarchive/git/2008/10/24/3789584>

  Git::Class
Depends on Moose, which seems an unnecessary dependency for a simple wrapper around Git. The startup penalty could become significant for command-line tools.

Although it supports "git init" and "git clone" (and has methods to call any Git command), it is mostly aimed at porcelain commands, and provides no way to control bidirectional commands (such as "git commit-tree").

  Git::Wrapper
Doesn't support streams or bidirectional commands.

AUTHOR
Philippe Bruhat (BooK), "<book at cpan.org>"

BUGS
Since version 1.17, "Git::Repository" delegates the actual command execution to "System::Command". Win32 support for that module is currently very bad (the test suite hangs in a few places). If you'd like better Win32 support for "Git::Repository", help me improve "System::Command"!

Please report any bugs or feature requests to "bug-git-repository at rt.cpan.org", or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Git-Repository <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Git-Repository>. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT
You can find documentation for this module with the perldoc command.

    perldoc Git::Repository

You can also look for information at:

•   RT: CPAN's request tracker

    http://rt.cpan.org/NoAuth/Bugs.html?Dist=Git-Repository <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Git-Repository>

•   AnnoCPAN: Annotated CPAN documentation

    http://annocpan.org/dist/Git-Repository <http://annocpan.org/dist/Git-Repository>

•   CPAN Ratings

    http://cpanratings.perl.org/d/Git-Repository <http://cpanratings.perl.org/d/Git-Repository>

•   Search CPAN

    http://search.cpan.org/dist/Git-Repository <http://search.cpan.org/dist/Git-Repository>

ACKNOWLEDGEMENTS
Thanks to Todd Rinalo, who wanted to add more methods to "Git::Repository", which made me look for a solution that would preserve the minimalism of "Git::Repository". The "::Plugin" interface is what I came up with.

COPYRIGHT
Copyright 2010-2011 Philippe Bruhat (BooK), all rights reserved.

LICENSE
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.