Git::Repository::Tutorial - Control git from Perl using Git::Repository
use Git::Repository; # do cool stuff with Git, using the following advice
A Git::Repository object represents an actual Git repository, against which you can run commands.
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.
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.
$command
@arguments
git
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Note that the old create() method is obsolete, warns and will be removed in a future version.
create()
Cloning works the same way:
Git::Repository->run( clone => $url => $dir ); $r = Git::Repository->new( $dir );
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.
croak()
carp()
Some Git porcelain commands provide additional information on STDERR. One typical example is git checkout:
STDERR
git checkout
$ git checkout mybranch Switched to branch 'mybranch'
The run() method of Git::Repository treats all output on STDERR as a warning. Therefore, the following code:
run()
$r->run( checkout => 'mybranch' );
will output a warning like this one:
Switched to branch 'mybranch' at myscript.pl line 10.
In such a case, you can use the quiet option to silence the warning for a single command:
quiet
$r->run( checkout => 'mybranch', { quiet => 1 } );
To silence all warnings, you can pass the quiet option during the creation of the original repository object:
my $r = Git::Repository->new( { quiet => 1 } );
This is not recommended, as it might hide important information from you.
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.
command()
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.
Use the input option:
input
my $commit = $r->run( 'commit-tree', $tree, '-p', $parent, { input => $message } );
Use the env option:
env
$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.
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.
format.pretty
medium
See also Git::Repository::Plugin::Log for adding to your Git::Repository objects a log() method that will parse the log output for you.
log()
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;
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:
sudo
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.
$r
sudo -u nobody git
Because Git::Repository automatically sets the GIT_DIR and GIT_WORK_TREE environment variables, some submodule sub-commands may fail. For example:
GIT_DIR
GIT_WORK_TREE
submodule
$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.
Basically, you need to recreate the cmp operator for Git versions, using the private _version_gt() method (which accepts two parameters):
cmp
_version_gt()
@sorted_versions = sort { Git::Repository::_version_gt( $a, $b ) || -Git::Repository::_version_gt( $b, $a ) } @versions;
Have a look at Git::Repository::Plugin and Git::Repository::Plugin::Log, to learn how to add your own methods to Git::Repository.
Philippe Bruhat (BooK), <book at cpan.org>
<book at cpan.org>
Copyright 2010-2012 Philippe Bruhat (BooK), all rights reserved.
This documentation is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Git::Repository, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Git::Repository
CPAN shell
perl -MCPAN -e shell install Git::Repository
For more information on module installation, please visit the detailed CPAN module installation guide.