Tools/Scripts/git-add-reviewer - WebKit - Git at Google

 #!/usr/bin/env perl
 #
 # Copyright (C) 2011 Apple Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 # 1.  Redistributions of source code must retain the above copyright
 #     notice, this list of conditions and the following disclaimer.
 # 2.  Redistributions in binary form must reproduce the above copyright
 #     notice, this list of conditions and the following disclaimer in the
 #     documentation and/or other materials provided with the distribution.
 #
 # THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
 # EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 # DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 # DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 # (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 # ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 use strict;
 use warnings;

 use File::Basename;
 use File::Temp ();
 use Getopt::Long;
 use POSIX;
 use IPC::Open2;

 use FindBin;
 use lib $FindBin::Bin;
 use webkitdirs;
 use VCSUtils;

 my $defaultReviewer = "NOBODY";

 sub addReviewer(\%);
 sub addReviewerToChangeLog($$$);
 sub addReviewerToCommitMessage($$$);
 sub changeLogsForCommit($);
 sub checkout($);
 sub cherryPick(\%);
 sub commit(;$);
 sub getConfigValue($);
 sub fail(;$);
 sub head();
 sub interactive();
 sub isAncestor($$);
 sub nonInteractive();
 sub rebaseOntoHead($$);
 sub requireCleanWorkTree();
 sub resetToCommit($);
 sub toCommit($);
 sub usage();
 sub writeCommitMessageToFile($);


 my $interactive = 0;
 my $showHelp = 0;
 my $rubberStamp = 0;

 my $programName = basename($0);
 my $usage = <<EOF;
 Usage: $programName -i|--interactive upstream
        $programName commit-ish reviewer

 Adds a reviewer to a git commit in a repository with WebKit-style commit logs
 and ChangeLogs.

 When run in interactive mode, `upstream` specifies the commit after which
 reviewers should be added.

 When run in non-interactive mode, `commit-ish` specifies the commit to which
 the `reviewer` will be added.

 Options:
   -h|--help          Display this message
   -i|--interactive   Interactive mode
   -s|--rubber-stamp  Change `Reviewed by` to `Rubber-stamped by`
 EOF

 my $getOptionsResult = GetOptions(
     'h|help' => \$showHelp,
     'i|interactive' => \$interactive,
     's|rubber-stamp' => \$rubberStamp,
 );

 my $gitDirectory = gitDirectory();

 usage() if !$getOptionsResult || $showHelp;

 requireCleanWorkTree();
 $interactive ? interactive() : nonInteractive();
 exit;

 sub interactive()
 {
     @ARGV == 1 or usage();

     my $upstream = toCommit($ARGV[0]);
     my $head = head();

     isAncestor($upstream, $head) or die "$ARGV[0] is not an ancestor of HEAD.";

     my @revlist = runCommandWithOutput('git', 'rev-list', '--reverse', '--pretty=oneline', "$upstream..");
     @revlist or die "Couldn't determine revisions";

     my $tempFile = new File::Temp(UNLINK => 1);
     foreach my $line (@revlist) {
         print $tempFile "$defaultReviewer : $line";
     }

     print $tempFile <<EOF;

 # Change 'NOBODY' to the reviewer for each commit
 #
 # If any line starts with "rs" followed by one or more spaces, then the phrase
 # "Reviewed by" is changed to "Rubber-stamped by" in the ChangeLog(s)/commit
 # message for that commit.
 #
 # Commits may be reordered
 # Omitted commits will be lost
 EOF

     close $tempFile;

     my $editor = $ENV{GIT_EDITOR} || getConfigValue("core.editor") || $ENV{VISUAL} || $ENV{EDITOR} || "vi";
     my $result = system "$editor \"" . $tempFile->filename . "\"";
     !($result >> 8) or die "Error spawning editor.";

     my @todo = ();
     open TEMPFILE, '<', $tempFile->filename or die "Error opening temp file.";
     foreach my $line (<TEMPFILE>) {
         next if $line =~ /^#/;
         $line =~ /^(rs\s+)?(.*)\s+:\s+([0-9a-fA-F]+)/ or next;
         push @todo, {rubberstamp => defined $1 && length $1, reviewer => $2, commit => $3};
     }
     close TEMPFILE;
     @todo or die "No revisions specified.";

     foreach my $item (@todo) {
         $item->{changeLogs} = changeLogsForCommit($item->{commit});
     }

     $result = system "git", "checkout", $upstream;
     !($result >> 8) or die "Error checking out $ARGV[0].";

     my $success = 1;
     foreach my $item (@todo) {
         $success = cherryPick(%{$item});
         $success or last;
         $success = addReviewer(%{$item});
         $success or last;
         $success = commit();
         $success or last;
     }

     unless ($success) {
         resetToCommit($head);
         exit 1;
     }

     $result = system "git", "branch", "-f", $head;
     !($result >> 8) or die "Error updating $head.";
     $result = system "git", "checkout", $head;
     exit WEXITSTATUS($result >> 8);
 }

 sub nonInteractive()
 {
     @ARGV == 2 or usage();

     my $commit = toCommit($ARGV[0]);
     my $reviewer = $ARGV[1];
     my $head = head();
     my $headCommit = toCommit($head);

     isAncestor($commit, $head) or die "$ARGV[0] is not an ancestor of HEAD.";
     chomp($reviewer);

     my %item = (
         reviewer => $reviewer,
         rubberstamp => $rubberStamp,
         commit => $commit,
     );

     $item{changeLogs} = changeLogsForCommit($commit);
     $item{changeLogs} or die;

     unless ((($commit eq $headCommit) or checkout($commit))
             && writeCommitMessageToFile("$gitDirectory/MERGE_MSG")
             && addReviewer(%item)
             && commit(1)
             && (($commit eq $headCommit) or rebaseOntoHead($commit, $head))) {
         resetToCommit($head);
         exit 1;
     }
 }

 sub usage()
 {
     print STDERR $usage;
     exit 1;
 }

 sub requireCleanWorkTree()
 {
     my $result = system("git rev-parse --verify HEAD > /dev/null") >> 8;
     $result ||= system(qw(git update-index --refresh)) >> 8;
     $result ||= system(qw(git diff-files --quiet)) >> 8;
     $result ||= system(qw(git diff-index --cached --quiet HEAD --)) >> 8;
     !$result or die "Working tree is dirty"
 }

 sub fail(;$)
 {
     my ($message) = @_;
     print STDERR $message, "\n" if defined $message;
     return 0;
 }

 sub cherryPick(\%)
 {
     my ($item) = @_;

     my $result = system "git cherry-pick -n $item->{commit} > /dev/null";
     !($result >> 8) or return fail("Failed to cherry-pick $item->{commit}");

     return 1;
 }

 sub addReviewer(\%)
 {
     my ($item) = @_;

     return 1 if $item->{reviewer} eq $defaultReviewer;

     foreach my $log (@{$item->{changeLogs}}) {
         addReviewerToChangeLog($item->{reviewer}, $item->{rubberstamp}, $log) or return fail();
     }

     addReviewerToCommitMessage($item->{reviewer}, $item->{rubberstamp}, "$gitDirectory/MERGE_MSG") or return fail();

     return 1;
 }

 sub commit(;$)
 {
     my ($amend) = @_;

     my @command = qw(git commit -F);
     push @command, "$gitDirectory/MERGE_MSG";
     push @command, "--amend" if $amend;
     my $result = system @command;
     !($result >> 8) or return fail("Failed to commit revision");

     return 1;
 }

 sub addReviewerToChangeLog($$$)
 {
     my ($reviewer, $rubberstamp, $log) = @_;

     return addReviewerToFile($reviewer, $rubberstamp, $log, 0);
 }

 sub addReviewerToCommitMessage($$$)
 {
     my ($reviewer, $rubberstamp, $log) = @_;

     return addReviewerToFile($reviewer, $rubberstamp, $log, 1);
 }

 sub addReviewerToFile
 {
     my ($reviewer, $rubberstamp, $log, $isCommitMessage) = @_;

     my $tempFile = new File::Temp(UNLINK => 1);

     open LOG, "<", $log or return fail("Couldn't open $log.");

     my $finished = 0;
     foreach my $line (<LOG>) {
         if (!$finished && $line =~ /NOBODY \(OOPS!\)/) {
             $line =~ s/NOBODY \(OOPS!\)/$reviewer/;
             $line =~ s/Reviewed/Rubber-stamped/ if $rubberstamp;
             $finished = 1 unless $isCommitMessage;
         }

         print $tempFile $line;
     }

     close $tempFile;
     close LOG or return fail("Couldn't close $log");

     my $result = system "mv", $tempFile->filename, $log;
     !($result >> 8) or return fail("Failed to rename $tempFile to $log");

     unless ($isCommitMessage) {
         my $result = system "git", "add", $log;
         !($result >> 8) or return fail("Failed to git add");
     }

     return 1;
 }

 sub head()
 {
     my $head = runCommandWithOutput('git', 'symbolic-ref', 'HEAD');
     $head =~ /^refs\/heads\/(.*)$/ or die "Couldn't determine current branch.";
     $head = $1;

     return $head;
 }

 sub isAncestor($$)
 {
     my ($ancestor, $descendant) = @_;

     chomp(my $mergeBase = runCommandWithOutput('git', 'merge-base', $ancestor, $descendant));
     return $mergeBase eq $ancestor;
 }

 sub toCommit($)
 {
     my ($arg) = @_;

     chomp(my $commit = runCommandWithOutput('git', 'rev-parse', $arg));
     return $commit;
 }

 sub changeLogsForCommit($)
 {
     my ($commit) = @_;

     my @files = runCommandWithOutput('git', 'diff', '-r', '--name-status', "$commit^", "$commit");
     @files or return fail("Couldn't determine changed files for $commit.");

     my @changeLogs = map { /^[ACMR]\s*(.*)/; makeFilePathRelative($1) } grep { /^[ACMR].*[^-]ChangeLog/ } @files;
     return \@changeLogs;
 }

 sub resetToCommit($)
 {
     my ($commit) = @_;

     my $result = system "git", "checkout", "-f", $commit;
     !($result >> 8) or return fail("Error checking out $commit.");

     return 1;
 }

 sub writeCommitMessageToFile($)
 {
     my ($file) = @_;

     open FILE, ">", $file or return fail("Couldn't open $file.");
     open MESSAGE, "-|", qw(git rev-list --max-count=1 --pretty=format:%B HEAD) or return fail("Error running git rev-list.");
     my $commitLine = <MESSAGE>;
     foreach my $line (<MESSAGE>) {
         print FILE $line;
     }
     close MESSAGE;
     close FILE or return fail("Couldn't close $file.");

     return 1;
 }

 sub rebaseOntoHead($$)
 {
     my ($upstream, $branch) = @_;

     my $result = system qw(git rebase --onto HEAD), $upstream, $branch;
     !$result or return fail("Couldn't rebase.");

     return 1;
 }

 sub checkout($)
 {
     my ($commit) = @_;

     my $result = system "git", "checkout", $commit;
     !$result or return fail("Error checking out $commit.");

     return 1;
 }

 sub getConfigValue($)
 {
     my ($variable) = @_;

     chomp(my $value = runCommandWithOutput('git', 'config', '--get', $variable));

     return $value;
 }

 sub runCommandWithOutput {
     my ($output, $input);

     my $pid = open2($output, $input, @_);

     waitpid($pid, 0);

     return <$output>;
 }
	#!/usr/bin/env perl
	#
	# Copyright (C) 2011 Apple Inc. All rights reserved.
	#
	# Redistribution and use in source and binary forms, with or without
	# modification, are permitted provided that the following conditions
	# are met:
	# 1. Redistributions of source code must retain the above copyright
	# notice, this list of conditions and the following disclaimer.
	# 2. Redistributions in binary form must reproduce the above copyright
	# notice, this list of conditions and the following disclaimer in the
	# documentation and/or other materials provided with the distribution.
	#
	# THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
	# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
	# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	# DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
	# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
	# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
	# ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
	# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	use strict;
	use warnings;

	use File::Basename;
	use File::Temp ();
	use Getopt::Long;
	use POSIX;
	use IPC::Open2;

	use FindBin;
	use lib $FindBin::Bin;
	use webkitdirs;
	use VCSUtils;

	my $defaultReviewer = "NOBODY";

	sub addReviewer(\%);
	sub addReviewerToChangeLog($$$);
	sub addReviewerToCommitMessage($$$);
	sub changeLogsForCommit($);
	sub checkout($);
	sub cherryPick(\%);
	sub commit(;$);
	sub getConfigValue($);
	sub fail(;$);
	sub head();
	sub interactive();
	sub isAncestor($$);
	sub nonInteractive();
	sub rebaseOntoHead($$);
	sub requireCleanWorkTree();
	sub resetToCommit($);
	sub toCommit($);
	sub usage();
	sub writeCommitMessageToFile($);


	my $interactive = 0;
	my $showHelp = 0;
	my $rubberStamp = 0;

	my $programName = basename($0);
	my $usage = <<EOF;
	Usage: $programName -i\|--interactive upstream
	$programName commit-ish reviewer

	Adds a reviewer to a git commit in a repository with WebKit-style commit logs
	and ChangeLogs.

	When run in interactive mode, `upstream` specifies the commit after which
	reviewers should be added.

	When run in non-interactive mode, `commit-ish` specifies the commit to which
	the `reviewer` will be added.

	Options:
	-h\|--help Display this message
	-i\|--interactive Interactive mode
	-s\|--rubber-stamp Change `Reviewed by` to `Rubber-stamped by`
	EOF

	my $getOptionsResult = GetOptions(
	'h\|help' => \$showHelp,
	'i\|interactive' => \$interactive,
	's\|rubber-stamp' => \$rubberStamp,
	);

	my $gitDirectory = gitDirectory();

	usage() if !$getOptionsResult \|\| $showHelp;

	requireCleanWorkTree();
	$interactive ? interactive() : nonInteractive();
	exit;

	sub interactive()
	{
	@ARGV == 1 or usage();

	my $upstream = toCommit($ARGV[0]);
	my $head = head();

	isAncestor($upstream, $head) or die "$ARGV[0] is not an ancestor of HEAD.";

	my @revlist = runCommandWithOutput('git', 'rev-list', '--reverse', '--pretty=oneline', "$upstream..");
	@revlist or die "Couldn't determine revisions";

	my $tempFile = new File::Temp(UNLINK => 1);
	foreach my $line (@revlist) {
	print $tempFile "$defaultReviewer : $line";
	}

	print $tempFile <<EOF;

	# Change 'NOBODY' to the reviewer for each commit
	#
	# If any line starts with "rs" followed by one or more spaces, then the phrase
	# "Reviewed by" is changed to "Rubber-stamped by" in the ChangeLog(s)/commit
	# message for that commit.
	#
	# Commits may be reordered
	# Omitted commits will be lost
	EOF

	close $tempFile;

	my $editor = $ENV{GIT_EDITOR} \|\| getConfigValue("core.editor") \|\| $ENV{VISUAL} \|\| $ENV{EDITOR} \|\| "vi";
	my $result = system "$editor \"" . $tempFile->filename . "\"";
	!($result >> 8) or die "Error spawning editor.";

	my @todo = ();
	open TEMPFILE, '<', $tempFile->filename or die "Error opening temp file.";
	foreach my $line (<TEMPFILE>) {
	next if $line =~ /^#/;
	$line =~ /^(rs\s+)?(.*)\s+:\s+([0-9a-fA-F]+)/ or next;
	push @todo, {rubberstamp => defined $1 && length $1, reviewer => $2, commit => $3};
	}
	close TEMPFILE;
	@todo or die "No revisions specified.";

	foreach my $item (@todo) {
	$item->{changeLogs} = changeLogsForCommit($item->{commit});
	}

	$result = system "git", "checkout", $upstream;
	!($result >> 8) or die "Error checking out $ARGV[0].";

	my $success = 1;
	foreach my $item (@todo) {
	$success = cherryPick(%{$item});
	$success or last;
	$success = addReviewer(%{$item});
	$success or last;
	$success = commit();
	$success or last;
	}

	unless ($success) {
	resetToCommit($head);
	exit 1;
	}

	$result = system "git", "branch", "-f", $head;
	!($result >> 8) or die "Error updating $head.";
	$result = system "git", "checkout", $head;
	exit WEXITSTATUS($result >> 8);
	}

	sub nonInteractive()
	{
	@ARGV == 2 or usage();

	my $commit = toCommit($ARGV[0]);
	my $reviewer = $ARGV[1];
	my $head = head();
	my $headCommit = toCommit($head);

	isAncestor($commit, $head) or die "$ARGV[0] is not an ancestor of HEAD.";
	chomp($reviewer);

	my %item = (
	reviewer => $reviewer,
	rubberstamp => $rubberStamp,
	commit => $commit,
	);

	$item{changeLogs} = changeLogsForCommit($commit);
	$item{changeLogs} or die;

	unless ((($commit eq $headCommit) or checkout($commit))
	&& writeCommitMessageToFile("$gitDirectory/MERGE_MSG")
	&& addReviewer(%item)
	&& commit(1)
	&& (($commit eq $headCommit) or rebaseOntoHead($commit, $head))) {
	resetToCommit($head);
	exit 1;
	}
	}

	sub usage()
	{
	print STDERR $usage;
	exit 1;
	}

	sub requireCleanWorkTree()
	{
	my $result = system("git rev-parse --verify HEAD > /dev/null") >> 8;
	$result \|\|= system(qw(git update-index --refresh)) >> 8;
	$result \|\|= system(qw(git diff-files --quiet)) >> 8;
	$result \|\|= system(qw(git diff-index --cached --quiet HEAD --)) >> 8;
	!$result or die "Working tree is dirty"
	}

	sub fail(;$)
	{
	my ($message) = @_;
	print STDERR $message, "\n" if defined $message;
	return 0;
	}

	sub cherryPick(\%)
	{
	my ($item) = @_;

	my $result = system "git cherry-pick -n $item->{commit} > /dev/null";
	!($result >> 8) or return fail("Failed to cherry-pick $item->{commit}");

	return 1;
	}

	sub addReviewer(\%)
	{
	my ($item) = @_;

	return 1 if $item->{reviewer} eq $defaultReviewer;

	foreach my $log (@{$item->{changeLogs}}) {
	addReviewerToChangeLog($item->{reviewer}, $item->{rubberstamp}, $log) or return fail();
	}

	addReviewerToCommitMessage($item->{reviewer}, $item->{rubberstamp}, "$gitDirectory/MERGE_MSG") or return fail();

	return 1;
	}

	sub commit(;$)
	{
	my ($amend) = @_;

	my @command = qw(git commit -F);
	push @command, "$gitDirectory/MERGE_MSG";
	push @command, "--amend" if $amend;
	my $result = system @command;
	!($result >> 8) or return fail("Failed to commit revision");

	return 1;
	}

	sub addReviewerToChangeLog($$$)
	{
	my ($reviewer, $rubberstamp, $log) = @_;

	return addReviewerToFile($reviewer, $rubberstamp, $log, 0);
	}

	sub addReviewerToCommitMessage($$$)
	{
	my ($reviewer, $rubberstamp, $log) = @_;

	return addReviewerToFile($reviewer, $rubberstamp, $log, 1);
	}

	sub addReviewerToFile
	{
	my ($reviewer, $rubberstamp, $log, $isCommitMessage) = @_;

	my $tempFile = new File::Temp(UNLINK => 1);

	open LOG, "<", $log or return fail("Couldn't open $log.");

	my $finished = 0;
	foreach my $line (<LOG>) {
	if (!$finished && $line =~ /NOBODY \(OOPS!\)/) {
	$line =~ s/NOBODY \(OOPS!\)/$reviewer/;
	$line =~ s/Reviewed/Rubber-stamped/ if $rubberstamp;
	$finished = 1 unless $isCommitMessage;
	}

	print $tempFile $line;
	}

	close $tempFile;
	close LOG or return fail("Couldn't close $log");

	my $result = system "mv", $tempFile->filename, $log;
	!($result >> 8) or return fail("Failed to rename $tempFile to $log");

	unless ($isCommitMessage) {
	my $result = system "git", "add", $log;
	!($result >> 8) or return fail("Failed to git add");
	}

	return 1;
	}

	sub head()
	{
	my $head = runCommandWithOutput('git', 'symbolic-ref', 'HEAD');
	$head =~ /^refs\/heads\/(.*)$/ or die "Couldn't determine current branch.";
	$head = $1;

	return $head;
	}

	sub isAncestor($$)
	{
	my ($ancestor, $descendant) = @_;

	chomp(my $mergeBase = runCommandWithOutput('git', 'merge-base', $ancestor, $descendant));
	return $mergeBase eq $ancestor;
	}

	sub toCommit($)
	{
	my ($arg) = @_;

	chomp(my $commit = runCommandWithOutput('git', 'rev-parse', $arg));
	return $commit;
	}

	sub changeLogsForCommit($)
	{
	my ($commit) = @_;

	my @files = runCommandWithOutput('git', 'diff', '-r', '--name-status', "$commit^", "$commit");
	@files or return fail("Couldn't determine changed files for $commit.");

	my @changeLogs = map { /^[ACMR]\s(.)/; makeFilePathRelative($1) } grep { /^[ACMR].*[^-]ChangeLog/ } @files;
	return \@changeLogs;
	}

	sub resetToCommit($)
	{
	my ($commit) = @_;

	my $result = system "git", "checkout", "-f", $commit;
	!($result >> 8) or return fail("Error checking out $commit.");

	return 1;
	}

	sub writeCommitMessageToFile($)
	{
	my ($file) = @_;

	open FILE, ">", $file or return fail("Couldn't open $file.");
	open MESSAGE, "-\|", qw(git rev-list --max-count=1 --pretty=format:%B HEAD) or return fail("Error running git rev-list.");
	my $commitLine = <MESSAGE>;
	foreach my $line (<MESSAGE>) {
	print FILE $line;
	}
	close MESSAGE;
	close FILE or return fail("Couldn't close $file.");

	return 1;
	}

	sub rebaseOntoHead($$)
	{
	my ($upstream, $branch) = @_;

	my $result = system qw(git rebase --onto HEAD), $upstream, $branch;
	!$result or return fail("Couldn't rebase.");

	return 1;
	}

	sub checkout($)
	{
	my ($commit) = @_;

	my $result = system "git", "checkout", $commit;
	!$result or return fail("Error checking out $commit.");

	return 1;
	}

	sub getConfigValue($)
	{
	my ($variable) = @_;

	chomp(my $value = runCommandWithOutput('git', 'config', '--get', $variable));

	return $value;
	}

	sub runCommandWithOutput {
	my ($output, $input);

	my $pid = open2($output, $input, @_);

	waitpid($pid, 0);

	return <$output>;
	}