path: root/IkiWiki/Rcs/git.pm

#!/usr/bin/perl

use warnings;
use strict;
use IkiWiki;
use Encode;
use open qw{:utf8 :std};

package IkiWiki;

my $sha1_pattern     = qr/[0-9a-fA-F]{40}/; # pattern to validate Git sha1sums
my $dummy_commit_msg = 'dummy commit';      # message to skip in recent changes

sub _safe_git (&@) { #{{{
    # Start a child process safely without resorting /bin/sh.
    # Return command output or success state (in scalar context).

    my ($error_handler, @cmdline) = @_;

    my $pid = open my $OUT, "-|";

    error("Cannot fork: $!") if !defined $pid;

    if (!$pid) {
        # In child.
        # Git commands want to be in wc.
        chdir $config{srcdir}
            or error("Cannot chdir to $config{srcdir}: $!");
        exec @cmdline or error("Cannot exec '@cmdline': $!");
    }
    # In parent.

    my @lines;
    while (<$OUT>) {
        chomp;
        push @lines, $_;
    }

    close $OUT;

    $error_handler->("'@cmdline' failed: $!") if $? && $error_handler;

    return wantarray ? @lines : ($? == 0);
}
# Convenient wrappers.
sub run_or_die ($@) { _safe_git(\&error, @_) }
sub run_or_cry ($@) { _safe_git(sub { warn @_ },  @_) }
sub run_or_non ($@) { _safe_git(undef,            @_) }
#}}}

sub _merge_past ($$$) { #{{{
    # Unlike with Subversion, Git cannot make a 'svn merge -rN:M file'.
    # Git merge commands work with the committed changes, except in the
    # implicit case of '-m' of git checkout(1).  So we should invent a
    # kludge here.  In principle, we need to create a throw-away branch
    # in preparing for the merge itself.  Since branches are cheap (and
    # branching is fast), this shouldn't cost high.
    #
    # The main problem is the presence of _uncommitted_ local changes.  One
    # possible approach to get rid of this situation could be that we first
    # make a temporary commit in the master branch and later restore the
    # initial state (this is possible since Git has the ability to undo a
    # commit, i.e. 'git reset --soft HEAD^').  The method can be summarized
    # as follows:
    #
    #   - create a diff of HEAD:current-sha1
    #   - dummy commit
    #   - create a dummy branch and switch to it
    #   - rewind to past (reset --hard to the current-sha1)
    #   - apply the diff and commit
    #   - switch to master and do the merge with the dummy branch
    #   - make a soft reset (undo the last commit of master)
    #
    # The above method has some drawbacks: (1) it needs a redundant commit
    # just to get rid of local changes, (2) somewhat slow because of the
    # required system forks.  Until someone points a more straight method
    # (which I would be grateful) I have implemented an alternative method.
    # In this approach, we hide all the modified files from Git by renaming
    # them (using the 'rename' builtin) and later restore those files in
    # the throw-away branch (that is, we put the files themselves instead
    # of applying a patch).

    my ($sha1, $file, $message) = @_;

    my @undo;      # undo stack for cleanup in case of an error
    my $conflict;  # file content with conflict markers

    eval {
        # Hide local changes from Git by renaming the modified file.
        # Relative paths must be converted to absolute for renaming.
        my ($target, $hidden) = (
            "$config{srcdir}/${file}", "$config{srcdir}/${file}.${sha1}"
        );
        rename($target, $hidden)
            or error("rename '$target' to '$hidden' failed: $!");
        # Ensure to restore the renamed file on error.
        push @undo, sub {
            return if ! -e "$hidden"; # already renamed
            rename($hidden, $target)
                or warn "rename '$hidden' to '$target' failed: $!";
        };

        my $branch = "throw_away_${sha1}"; # supposed to be unique

        # Create a throw-away branch and rewind backward.
        push @undo, sub { run_or_cry('git', 'branch', '-D', $branch) };
        run_or_die('git', 'branch', $branch, $sha1);

        # Switch to throw-away branch for the merge operation.
        push @undo, sub {
            if (!run_or_cry('git', 'checkout', $config{gitmaster_branch})) {
                run_or_cry('git', 'checkout','-f',$config{gitmaster_branch});
            }
        };
        run_or_die('git', 'checkout', $branch);

        # Put the modified file in _this_ branch.
        rename($hidden, $target)
            or error("rename '$hidden' to '$target' failed: $!");

        # _Silently_ commit all modifications in the current branch.
        run_or_non('git', 'commit', '-m', $message, '-a');
        # ... and re-switch to master.
        run_or_die('git', 'checkout', $config{gitmaster_branch});

        # Attempt to merge without complaining.
        if (!run_or_non('git', 'pull', '--no-commit', '.', $branch)) {
            $conflict = readfile($target);
            run_or_die('git', 'reset', '--hard');
        }
    };
    my $failure = $@;

    # Process undo stack (in reverse order).  By policy cleanup
    # actions should normally print a warning on failure.
    while (my $handle = pop @undo) {
        $handle->();
    }

    error("Git merge failed!\n$failure\n") if $failure;

    return $conflict;
} #}}}

sub _parse_diff_tree ($@) { #{{{
    # Parse the raw diff tree chunk and return the info hash.
    # See git-diff-tree(1) for the syntax.

    my ($prefix, $dt_ref) = @_;

    # End of stream?
    return if !defined @{ $dt_ref } ||
          !defined @{ $dt_ref }[0] || !length @{ $dt_ref }[0];

    my %ci;
    # Header line.
    while (my $line = shift @{ $dt_ref }) {
        return if $line !~ m/^(.+) ($sha1_pattern)/;

        my $sha1 = $2;
        $ci{'sha1'} = $sha1;
        last;
    }

    # Identification lines for the commit.
    while (my $line = shift @{ $dt_ref }) {
        # Regexps are semi-stolen from gitweb.cgi.
        if ($line =~ m/^tree ([0-9a-fA-F]{40})$/) {
            $ci{'tree'} = $1;
        }
        elsif ($line =~ m/^parent ([0-9a-fA-F]{40})$/) {
            # XXX: collecting in reverse order
            push @{ $ci{'parents'} }, $1;
        }
        elsif ($line =~ m/^(author|committer) (.*) ([0-9]+) (.*)$/) {
            my ($who, $name, $epoch, $tz) =
               ($1,   $2,    $3,     $4 );

            $ci{  $who          } = $name;
            $ci{ "${who}_epoch" } = $epoch;
            $ci{ "${who}_tz"    } = $tz;

            if ($name =~ m/^([^<]+) <([^@>]+)/) {
                my ($fullname, $username) = ($1, $2);
                $ci{"${who}_fullname"}    = $fullname;
                $ci{"${who}_username"}    = $username;
            }
            else {
                $ci{"${who}_fullname"} =
                    $ci{"${who}_username"} = $name;
            }
        }
        elsif ($line =~ m/^$/) {
            # Trailing empty line signals next section.
            last;
        }
    }

    debug("No 'tree' seen in diff-tree output") if !defined $ci{'tree'};

    if (defined $ci{'parents'}) {
        $ci{'parent'} = @{ $ci{'parents'} }[0];
    }
    else {
        $ci{'parent'} = 0 x 40;
    }

    # Commit message.
    while (my $line = shift @{ $dt_ref }) {
        if ($line =~ m/^$/) {
            # Trailing empty line signals next section.
            last;
        };
        $line =~ s/^    //;
        push @{ $ci{'comment'} }, $line;
    }

    # Modified files.
    while (my $line = shift @{ $dt_ref }) {
        if ($line =~ m{^
            (:+)       # number of parents
            ([^\t]+)\t # modes, sha1, status
            (.*)       # file names
        $}xo) {
            my $num_parents = length $1;
            my @tmp = split(" ", $2);
            my ($file, $file_to) = split("\t", $3);
            my @mode_from = splice(@tmp, 0, $num_parents);
            my $mode_to = shift(@tmp);
            my @sha1_from = splice(@tmp, 0, $num_parents);
            my $sha1_to = shift(@tmp);
            my $status = shift(@tmp);

            if ($file =~ m/^"(.*)"$/) {
                ($file=$1) =~ s/\\([0-7]{1,3})/chr(oct($1))/eg;
            }
            $file =~ s/^\Q$prefix\E//;
            if (length $file) {
                push @{ $ci{'details'} }, {
                    'file'      => decode_utf8($file),
                    'sha1_from' => $sha1_from[0],
                    'sha1_to'   => $sha1_to,
                };
            }
            next;
        };
        last;
    }

    return \%ci;
} #}}}

sub git_commit_info ($;$) { #{{{
    # Return an array of commit info hashes of num commits (default: 1)
    # starting from the given sha1sum.

    my ($sha1, $num) = @_;

    $num ||= 1;

    my @raw_lines = run_or_die('git', 'log', "--max-count=$num", 
        '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c',
        '-r', $sha1, '--', '.');
    my ($prefix) = run_or_die('git', 'rev-parse', '--show-prefix');

    my @ci;
    while (my $parsed = _parse_diff_tree(($prefix or ""), \@raw_lines)) {
        push @ci, $parsed;
    }

    warn "Cannot parse commit info for '$sha1' commit" if !@ci;

    return wantarray ? @ci : $ci[0];
} #}}}

sub git_sha1 (;$) { #{{{
    # Return head sha1sum (of given file).

    my $file = shift || q{--};

    # Ignore error since a non-existing file might be given.
    my ($sha1) = run_or_non('git', 'rev-list', '--max-count=1', 'HEAD', $file);
    if ($sha1) {
        ($sha1) = $sha1 =~ m/($sha1_pattern)/; # sha1 is untainted now
    } else { debug("Empty sha1sum for '$file'.") }
    return defined $sha1 ? $sha1 : q{};
} #}}}

sub rcs_update () { #{{{
    # Update working directory.

    if (length $config{gitorigin_branch}) {
        run_or_cry('git', 'pull', $config{gitorigin_branch});
    }
} #}}}

sub rcs_prepedit ($) { #{{{
    # Return the commit sha1sum of the file when editing begins.
    # This will be later used in rcs_commit if a merge is required.

    my ($file) = @_;

    return git_sha1($file);
} #}}}

sub rcs_commit ($$$;$$) { #{{{
    # Try to commit the page; returns undef on _success_ and
    # a version of the page with the rcs's conflict markers on
    # failure.

    my ($file, $message, $rcstoken, $user, $ipaddr) = @_;

    if (defined $user) {
        $message = "web commit by $user" .
            (length $message ? ": $message" : "");
    }
    elsif (defined $ipaddr) {
        $message = "web commit from $ipaddr" .
            (length $message ? ": $message" : "");
    }

    # XXX: Wiki directory is in the unlocked state when starting this
    # action.  But it takes time for a Git process to finish its job
    # (especially if a merge required), so we must re-lock to prevent
    # race conditions.  Only when the time of the real commit action
    # (i.e. git push) comes, we'll unlock the directory.
    lockwiki();

    # Check to see if the page has been changed by someone else since
    # rcs_prepedit was called.
    my $cur    = git_sha1($file);
    my ($prev) = $rcstoken =~ /^($sha1_pattern)$/; # untaint

    if (defined $cur && defined $prev && $cur ne $prev) {
        my $conflict = _merge_past($prev, $file, $dummy_commit_msg);
        return $conflict if defined $conflict;
    }

    # git commit returns non-zero if file has not been really changed.
    # so we should ignore its exit status (hence run_or_non).
    $message = possibly_foolish_untaint($message);
    if (run_or_non('git', 'commit', '-q', '-m', $message, '-i', $file)) {
        unlockwiki();
        if (length $config{gitorigin_branch}) {
            run_or_cry('git', 'push', $config{gitorigin_branch});
        }
    }

    return undef; # success
} #}}}

sub rcs_add ($) { # {{{
    # Add file to archive.

    my ($file) = @_;

    run_or_cry('git', 'add', $file);
} #}}}

sub rcs_recentchanges ($) { #{{{
    # List of recent changes.

    my ($num) = @_;

    eval q{use Date::Parse};
    error($@) if $@;

    my @rets;
    foreach my $ci (git_commit_info('HEAD', $num)) {
        # Skip redundant commits.
        next if (@{$ci->{'comment'}}[0] eq $dummy_commit_msg);

        my ($sha1, $when) = (
            $ci->{'sha1'},
            $ci->{'author_epoch'}
        );

        my (@pages, @messages);
        foreach my $detail (@{ $ci->{'details'} }) {
            my $file = $detail->{'file'};

            my $diffurl = $config{'diffurl'};
            $diffurl =~ s/\[\[file\]\]/$file/go;
            $diffurl =~ s/\[\[sha1_parent\]\]/$ci->{'parent'}/go;
            $diffurl =~ s/\[\[sha1_from\]\]/$detail->{'sha1_from'}/go;
            $diffurl =~ s/\[\[sha1_to\]\]/$detail->{'sha1_to'}/go;

            push @pages, {
                page => pagename($file),
                diffurl => $diffurl,
            };
        }
        push @messages, { line => $_ } foreach @{$ci->{'comment'}};

        my ($user, $type) = (q{}, "web");

        if (defined $messages[0] &&
            $messages[0]->{line} =~ m/$config{web_commit_regexp}/) {
            $user = defined $2 ? "$2" : "$3";
            $messages[0]->{line} = $4;
        }
        else {
            $type ="git";
            $user = $ci->{'author_username'};
        }

        push @rets, {
            rev        => $sha1,
            user       => $user,
            committype => $type,
            when       => $when,
            message    => [@messages],
            pages      => [@pages],
        } if @pages;

        last if @rets >= $num;
    }

    return @rets;
} #}}}

sub rcs_getctime ($) { #{{{
    my $file=shift;
    # Remove srcdir prefix
    $file =~ s/^\Q$config{srcdir}\E\/?//;

    my $sha1  = git_sha1($file);
    my $ci    = git_commit_info($sha1);
    my $ctime = $ci->{'author_epoch'};
    debug("ctime for '$file': ". localtime($ctime));

    return $ctime;
} #}}}

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