path: root/perl/Git.pm

=head1 NAME

Git - Perl interface to the Git version control system

=cut


package Git;

use strict;


BEGIN {

our ($VERSION, @ISA, @EXPORT, @EXPORT_OK);

# Totally unstable API.
$VERSION = '0.01';


=head1 SYNOPSIS

  use Git;

  my $version = Git::command_oneline('version');

  git_cmd_try { Git::command_noisy('update-server-info') }
              '%s failed w/ code %d';

  my $repo = Git->repository (Directory => '/srv/git/cogito.git');


  my @revs = $repo->command('rev-list', '--since=last monday', '--all');

  my ($fh, $c) = $repo->command_output_pipe('rev-list', '--since=last monday', '--all');
  my $lastrev = <$fh>; chomp $lastrev;
  $repo->command_close_pipe($fh, $c);

  my $lastrev = $repo->command_oneline( [ 'rev-list', '--all' ],
                                        STDERR => 0 );

=cut


require Exporter;

@ISA = qw(Exporter);

@EXPORT = qw(git_cmd_try);

# Methods which can be called as standalone functions as well:
@EXPORT_OK = qw(command command_oneline command_noisy
                command_output_pipe command_input_pipe command_close_pipe
                version exec_path hash_object git_cmd_try);


=head1 DESCRIPTION

This module provides Perl scripts easy way to interface the Git version control
system. The modules have an easy and well-tested way to call arbitrary Git
commands; in the future, the interface will also provide specialized methods
for doing easily operations which are not totally trivial to do over
the generic command interface.

While some commands can be executed outside of any context (e.g. 'version'
or 'init'), most operations require a repository context, which in practice
means getting an instance of the Git object using the repository() constructor.
(In the future, we will also get a new_repository() constructor.) All commands
called as methods of the object are then executed in the context of the
repository.

Part of the "repository state" is also information about path to the attached
working copy (unless you work with a bare repository). You can also navigate
inside of the working copy using the C<wc_chdir()> method. (Note that
the repository object is self-contained and will not change working directory
of your process.)

TODO: In the future, we might also do

	my $remoterepo = $repo->remote_repository (Name => 'cogito', Branch => 'master');
	$remoterepo ||= Git->remote_repository ('http://git.or.cz/cogito.git/');
	my @refs = $remoterepo->refs();

Currently, the module merely wraps calls to external Git tools. In the future,
it will provide a much faster way to interact with Git by linking directly
to libgit. This should be completely opaque to the user, though (performance
increate nonwithstanding).

=cut


use Carp qw(carp croak); # but croak is bad - throw instead
use Error qw(:try);
use Cwd qw(abs_path);

}


=head1 CONSTRUCTORS

=over 4

=item repository ( OPTIONS )

=item repository ( DIRECTORY )

=item repository ()

Construct a new repository object.
C<OPTIONS> are passed in a hash like fashion, using key and value pairs.
Possible options are:

B<Repository> - Path to the Git repository.

B<WorkingCopy> - Path to the associated working copy; not strictly required
as many commands will happily crunch on a bare repository.

B<WorkingSubdir> - Subdirectory in the working copy to work inside.
Just left undefined if you do not want to limit the scope of operations.

B<Directory> - Path to the Git working directory in its usual setup.
The C<.git> directory is searched in the directory and all the parent
directories; if found, C<WorkingCopy> is set to the directory containing
it and C<Repository> to the C<.git> directory itself. If no C<.git>
directory was found, the C<Directory> is assumed to be a bare repository,
C<Repository> is set to point at it and C<WorkingCopy> is left undefined.
If the C<$GIT_DIR> environment variable is set, things behave as expected
as well.

You should not use both C<Directory> and either of C<Repository> and
C<WorkingCopy> - the results of that are undefined.

Alternatively, a directory path may be passed as a single scalar argument
to the constructor; it is equivalent to setting only the C<Directory> option
field.

Calling the constructor with no options whatsoever is equivalent to
calling it with C<< Directory => '.' >>. In general, if you are building
a standard porcelain command, simply doing C<< Git->repository() >> should
do the right thing and setup the object to reflect exactly where the user
is right now.

=cut

sub repository {
	my $class = shift;
	my @args = @_;
	my %opts = ();
	my $self;

	if (defined $args[0]) {
		if ($#args % 2 != 1) {
			# Not a hash.
			$#args == 0 or throw Error::Simple("bad usage");
			%opts = ( Directory => $args[0] );
		} else {
			%opts = @args;
		}
	}

	if (not defined $opts{Repository} and not defined $opts{WorkingCopy}) {
		$opts{Directory} ||= '.';
	}

	if ($opts{Directory}) {
		-d $opts{Directory} or throw Error::Simple("Directory not found: $!");

		my $search = Git->repository(WorkingCopy => $opts{Directory});
		my $dir;
		try {
			$dir = $search->command_oneline(['rev-parse', '--git-dir'],
			                                STDERR => 0);
		} catch Git::Error::Command with {
			$dir = undef;
		};

		if ($dir) {
			$dir =~ m#^/# or $dir = $opts{Directory} . '/' . $dir;
			$opts{Repository} = $dir;

			# If --git-dir went ok, this shouldn't die either.
			my $prefix = $search->command_oneline('rev-parse', '--show-prefix');
			$dir = abs_path($opts{Directory}) . '/';
			if ($prefix) {
				if (substr($dir, -length($prefix)) ne $prefix) {
					throw Error::Simple("rev-parse confused me - $dir does not have trailing $prefix");
				}
				substr($dir, -length($prefix)) = '';
			}
			$opts{WorkingCopy} = $dir;
			$opts{WorkingSubdir} = $prefix;

		} else {
			# A bare repository? Let's see...
			$dir = $opts{Directory};

			unless (-d "$dir/refs" and -d "$dir/objects" and -e "$dir/HEAD") {
				# Mimick git-rev-parse --git-dir error message:
				throw Error::Simple('fatal: Not a git repository');
			}
			my $search = Git->repository(Repository => $dir);
			try {
				$search->command('symbolic-ref', 'HEAD');
			} catch Git::Error::Command with {
				# Mimick git-rev-parse --git-dir error message:
				throw Error::Simple('fatal: Not a git repository');
			}

			$opts{Repository} = abs_path($dir);
		}

		delete $opts{Directory};
	}

	$self = { opts => \%opts };
	bless $self, $class;
}


=back

=head1 METHODS

=over 4

=item command ( COMMAND [, ARGUMENTS... ] )

=item command ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )

Execute the given Git C<COMMAND> (specify it without the 'git-'
prefix), optionally with the specified extra C<ARGUMENTS>.

The second more elaborate form can be used if you want to further adjust
the command execution. Currently, only one option is supported:

B<STDERR> - How to deal with the command's error output. By default (C<undef>)
it is delivered to the caller's C<STDERR>. A false value (0 or '') will cause
it to be thrown away. If you want to process it, you can get it in a filehandle
you specify, but you must be extremely careful; if the error output is not
very short and you want to read it in the same process as where you called
C<command()>, you are set up for a nice deadlock!

The method can be called without any instance or on a specified Git repository
(in that case the command will be run in the repository context).

In scalar context, it returns all the command output in a single string
(verbatim).

In array context, it returns an array containing lines printed to the
command's stdout (without trailing newlines).

In both cases, the command's stdin and stderr are the same as the caller's.

=cut

sub command {
	my ($fh, $ctx) = command_output_pipe(@_);

	if (not defined wantarray) {
		# Nothing to pepper the possible exception with.
		_cmd_close($fh, $ctx);

	} elsif (not wantarray) {
		local $/;
		my $text = <$fh>;
		try {
			_cmd_close($fh, $ctx);
		} catch Git::Error::Command with {
			# Pepper with the output:
			my $E = shift;
			$E->{