Git::Repository::Tutorial(3p)

NAME
Git::Repository::Tutorial - Control git from Perl using Git::Repository

SYNOPSIS
    use Git::Repository;

    # do cool stuff with Git, using the following advice

HOW-TO
A "Git::Repository" object represents an actual Git repository, against which you can run commands.

  Obtain a Git::Repository object from an existing repository
If your script is expected to run against a repository in the current directory (like most Git commands), let "Git::Repository" handle the magic:

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

If the repository has a working copy (work tree):

    $r = Git::Repository->new( work_tree => $dir );

If the repository is a bare repository, or you prefer to provide the .git directory location:

    $r = Git::Repository->new( git_dir => $gitdir );

If the work tree and the git directory are in unrelated locations, you can also provide both:

    $r = Git::Repository->new( work_tree => $dir, git_dir => $gitdir );

The constructor also accepts an option hash. The various options are detailed in the manual page for "Git::Repository::Command".

  Run any git command
Git commands can be run against an existing "Git::Repository" object, or against the class itself (in which case, git will try to deduce its context from the current directory and the environment).

The pattern for running commands is always the same:

    $r->run( $command => @arguments, \%options );

The $command and @arguments are identical to those you'd pass to the "git" command-line tool. The options hash contains options, as described in the manual page for "Git::Repository::Command".

  Create a new repository
Sometime, you'll need to create the Git repository from scratch:

    # git version 1.6.5 and above
    Git::Repository->run( init => $dir );
    $r = Git::Repository->new( work_tree => $dir );

    # any older git requires the command to be run in the work tree,
    # so we use the cwd option
    Git::Repository->run( init => { cwd => $dir } );
    $r = Git::Repository->new( work_tree => $dir );

Note that the old "create()" method is obsolete, warns and will be removed in a future version.

  Clone a repository
Cloning works the same way:

    Git::Repository->run( clone => $url => $dir );
    $r = Git::Repository->new( $dir );

  Run a simple command
When you don't really care about the output of the command, just call it:

    $r->run( add => '.' );
    $r->run( commit => '-m', 'my commit message' );

In case of an error or warning, "Git::Repository" will "croak()" or "carp()" appropriately.

  Process normal and error output
The "run()" command doesn't capture stderr: it only warns (or dies) if something was printed on it. To be able to actually capture error output, "command()" must be used.

    my $cmd = $r->command( @cmd );
    my @errput = $cmd->stderr->getlines();
    $cmd->close;

"run()" also captures all output at once, which can lead to unnecessary memory consumption when capturing the output of some really verbose commands.

    my $cmd = $r->command( log => '--pretty=oneline', '--all' );
    my $log = $cmd->stdout;
    while (<$log>) {
        ...;
    }
    $cmd->close;

Of course, as soon as one starts reading and writing to an external process' communication handles, a risk of blocking exists. Caveat emptor.

  Provide input on standard input
Use the "input" option:

    my $commit = $r->run( 'commit-tree', $tree, '-p', $parent,
        { input => $message } );

  Change the environment of a command
Use the "env" option:

    $r->run(
        'commit', '-m', 'log message',
        {   env => {
                GIT_COMMITTER_NAME  => 'Git::Repository',
                GIT_COMMITTER_EMAIL => 'book@cpan.org',
            },
        },
    );

See Git::Repository::Command for other available options.

  Process the output of git log
When creating a tool that needs to process the output of git log, you should always define precisely the expected format using the --pretty option, and choose a format that is easy to parse.

Assuming git log will output the default format will eventually lead to problems, for example when the user's git configuration defines "format.pretty" to be something else than the default of "medium".

  Process the output of git shortlog
git shortlog behaves differently when it detects it's not attached to a terminal. In that case, it just tries to read some git log output from its standard input.

So this oneliner will hang, because git shortlog is waiting for some data from the program connected to its standard input (the oneliner):

    perl -MGit::Repository -le 'print scalar Git::Repository->run( shortlog => -5 )'

Whereas this one will "work" (as in "immediately return with no output"):

    perl -MGit::Repository -le 'print scalar Git::Repository->run( shortlog => -5, { input => "" } )'

So, you need to give git shortlog some input (from git log):

    perl -MGit::Repository -le 'print scalar Git::Repository->run( shortlog => { input => scalar Git::Repository->run( log => -5 ) } )'

If the log output is large, you'll probably be better off with something like the following:

    use Git::Repository;

    # start both git commands
    my $log = Git::Repository->command('log')->stdout;
    my $cmd = Git::Repository->command( shortlog => -ens );

    # feed one with the output of the other
    my $in = $cmd->stdin;
    print {$in} $_ while <$log>;
    close $in;

    # and do something with the output
    print $cmd->stdout->getlines;

  Wrap git in a sudo call
If for a given repository you want to wrap all calls to git in a "sudo" call, you can use the "git" option with an array ref:

    my $r = Git::Repository->new( { git => [qw( sudo -u nobody git )] } );

In this case, every call to git from $r will actually call "sudo -u nobody git".

  Use submodules
Because "Git::Repository" automatically sets the "GIT_DIR" and "GIT_WORK_TREE" environment variables, some "submodule" sub-commands may fail. For example:

    $r->run( submodule => add => $repository => 'sub' );

will give the following error:

    error: pathspec 'sub' did not match any file(s) known to git.

To avoid this error, you should enforce the removal of the "GIT_WORK_TREE" variable from the environment in which the command is run:

    $r->run(
        submodule => add => $repository => 'sub',
        { env => { GIT_WORK_TREE => undef } }
    );

Note that "System::Command" version 1.04 is required to be able to remove variables from the environment.

  Sort git versions
Basically, you need to recreate the "cmp" operator for Git versions, using the private "_version_gt()" method (which accepts two parameters):

    @sorted_versions = sort {
        Git::Repository::_version_gt( $a, $b )
            || -Git::Repository::_version_gt( $b, $a )
    } @versions;

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

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

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