Linux Blog


Section: User Contributed Perl Documentation (3)
Updated: 2007-09-29
Index Return to Main Contents


Git - Perl interface to the Git version control system  


  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 );



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 "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 ('');
        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).  


repository ( OPTIONS )
repository ( DIRECTORY )
repository ()
Construct a new repository object. "OPTIONS" are passed in a hash like fashion, using key and value pairs. Possible options are:

Repository - Path to the Git repository.

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

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

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

You should not use both "Directory" and either of "Repository" and "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 "Directory" option field.

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



command ( COMMAND [, ARGUMENTS... ] )
command ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
Execute the given Git "COMMAND" (specify it without the 'git-' prefix), optionally with the specified extra "ARGUMENTS".

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

STDERR - How to deal with the command's error output. By default ("undef") it is delivered to the caller's "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 "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.

command_oneline ( COMMAND [, ARGUMENTS... ] )
command_oneline ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
Execute the given "COMMAND" in the same way as command() does but always return a scalar string containing the first line of the command's standard output.
command_output_pipe ( COMMAND [, ARGUMENTS... ] )
command_output_pipe ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
Execute the given "COMMAND" in the same way as command() does but return a pipe filehandle from which the command output can be read.

The function can return "($pipe, $ctx)" in array context. See "command_close_pipe()" for details.

command_input_pipe ( COMMAND [, ARGUMENTS... ] )
command_input_pipe ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
Execute the given "COMMAND" in the same way as command_output_pipe() does but return an input pipe filehandle instead; the command output is not captured.

The function can return "($pipe, $ctx)" in array context. See "command_close_pipe()" for details.

command_close_pipe ( PIPE [, CTX ] )
Close the "PIPE" as returned from "command_*_pipe()", checking whether the command finished successfully. The optional "CTX" argument is required if you want to see the command name in the error message, and it is the second value returned by "command_*_pipe()" when called in array context. The call idiom is:

        my ($fh, $ctx) = $r->command_output_pipe('status');
        while (<$fh>) { ... }
        $r->command_close_pipe($fh, $ctx);

Note that you should not rely on whatever actually is in "CTX"; currently it is simply the command name but in future the context might have more complicated structure.

command_noisy ( COMMAND [, ARGUMENTS... ] )
Execute the given "COMMAND" in the same way as command() does but do not capture the command output - the standard output is not redirected and goes to the standard output of the caller application.

While the method is called command_noisy(), you might want to as well use it for the most silent Git commands which you know will never pollute your stdout but you want to avoid the overhead of the pipe setup when calling them.

The function returns only after the command has finished running.

version ()
Return the Git version in use.
exec_path ()
Return path to the Git sub-command executables (the same as "git --exec-path"). Useful mostly only internally.
repo_path ()
Return path to the git repository. Must be called on a repository instance.
wc_path ()
Return path to the working copy. Must be called on a repository instance.
wc_subdir ()
Return path to the subdirectory inside of a working copy. Must be called on a repository instance.
wc_chdir ( SUBDIR )
Change the working copy subdirectory to work within. The "SUBDIR" is relative to the working copy root directory (not the current subdirectory). Must be called on a repository instance attached to a working copy and the directory must exist.
config ( VARIABLE )
Retrieve the configuration "VARIABLE" in the same manner as "config" does. In scalar context requires the variable to be set only one time (exception is thrown otherwise), in array context returns allows the variable to be set multiple times and returns all the values.

Must be called on a repository instance.

This currently wraps command('config') so it is not so fast.

config_bool ( VARIABLE )
Retrieve the bool configuration "VARIABLE". The return value is usable as a boolean in perl (and "undef" if it's not defined, of course).

Must be called on a repository instance.

This currently wraps command('config') so it is not so fast.

ident ( TYPE | IDENTSTR )
ident_person ( TYPE | IDENTSTR | IDENTARRAY )
This suite of functions retrieves and parses ident information, as stored in the commit and tag objects or produced by "var GIT_type_IDENT" (thus "TYPE" can be either author or committer; case is insignificant).

The "ident" method retrieves the ident information from "git-var" and either returns it as a scalar string or as an array with the fields parsed. Alternatively, it can take a prepared ident string (e.g. from the commit object) and just parse it.

"ident_person" returns the person part of the ident - name and email; it can take the same arguments as "ident" or the array returned by "ident".

The synopsis is like:

        my ($name, $email, $time_tz) = ident('author');
        "$name <$email>" eq ident_person('author');
        "$name <$email>" eq ident_person($name);
        $time_tz =~ /^\d+ [+-]\d{4}$/;

Both methods must be called on a repository instance.

hash_object ( TYPE, FILENAME )
Compute the SHA1 object id of the given "FILENAME" (or data waiting in "FILEHANDLE") considering it is of the "TYPE" object type ("blob", "commit", "tree").

The method can be called without any instance or on a specified Git repository, it makes zero difference.

The function returns the SHA1 hash.



All functions are supposed to throw Perl exceptions in case of errors. See the Error module on how to catch those. Most exceptions are mere Error::Simple instances.

However, the "command()", "command_oneline()" and "command_noisy()" functions suite can throw "Git::Error::Command" exceptions as well: those are thrown when the external command returns an error code and contain the error code as well as access to the captured command's output. The exception class provides the usual "stringify" and "value" (command's exit code) methods and in addition also a "cmd_output" method that returns either an array or a string with the captured command output (depending on the original function call context; "command_noisy()" returns "undef") and $<cmdline> which returns the command and its arguments (but without proper quoting).

Note that the "command_*_pipe()" functions cannot throw this exception since it has no idea whether the command failed or not. You will only find out at the time you "close" the pipe; if you want to have that automated, use "command_close_pipe()", which can throw the exception.

git_cmd_try { CODE } ERRMSG
This magical statement will automatically catch any "Git::Error::Command" exceptions thrown by "CODE" and make your program die with "ERRMSG" on its lips; the message will have %s substituted for the command line and %d for the exit status. This statement is useful mostly for producing more user-friendly error messages.

In case of no exception caught the statement returns "CODE"'s return value.

Note that this is the only auto-exported function.



Copyright 2006 by Petr Baudis <>.

This module is free software; it may be used, copied, modified and distributed under the terms of the GNU General Public Licence, either version 2, or (at your option) any later version.




Random Man Pages: