Add automated test for using the CGI with git, including CVE-2016-10026

[git.ikiwiki.info.git] / IkiWiki / Plugin / git.pm

diff --git a/IkiWiki/Plugin/git.pm b/IkiWiki/Plugin/git.pm
index 3db4af7291b0d11dcdf8bc89386b93133c963e10..021ee726cb86b171ef686a6c7fe880d517b0c30e 100644 (file)
--- a/IkiWiki/Plugin/git.pm
+++ b/IkiWiki/Plugin/git.pm
@@ -5,11 +5,11 @@ use warnings;
 use strict;
 use IkiWiki;
 use Encode;
 use strict;
 use IkiWiki;
 use Encode;

+use URI::Escape q{uri_escape_utf8};

 use open qw{:utf8 :std};
 
 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
 use open qw{:utf8 :std};
 
 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

-my $git_dir=undef;

 
 sub import {
        hook(type => "checkconfig", id => "git", call => \&checkconfig);
 
 sub import {
        hook(type => "checkconfig", id => "git", call => \&checkconfig);


@@ -29,6 +29,8 @@ sub import {
        hook(type => "rcs", id => "rcs_receive", call => \&rcs_receive);
        hook(type => "rcs", id => "rcs_preprevert", call => \&rcs_preprevert);
        hook(type => "rcs", id => "rcs_revert", call => \&rcs_revert);
        hook(type => "rcs", id => "rcs_receive", call => \&rcs_receive);
        hook(type => "rcs", id => "rcs_preprevert", call => \&rcs_preprevert);
        hook(type => "rcs", id => "rcs_revert", call => \&rcs_revert);

+       hook(type => "rcs", id => "rcs_find_changes", call => \&rcs_find_changes);
+       hook(type => "rcs", id => "rcs_get_current_rev", call => \&rcs_get_current_rev);

 }
 
 sub checkconfig () {
 }
 
 sub checkconfig () {


@@ -151,11 +153,23 @@ sub genwrapper {
        }
 }
 
        }
 }
 

+my $git_dir=undef;
+my $prefix=undef;
+
+sub in_git_dir ($$) {
+       $git_dir=shift;
+       my @ret=shift->();
+       $git_dir=undef;
+       $prefix=undef;
+       return @ret;
+}
+

 sub safe_git (&@) {
 sub safe_git (&@) {

-       # Start a child process safely without resorting /bin/sh.
-       # Return command output or success state (in scalar context).
+       # Start a child process safely without resorting to /bin/sh.
+       # Returns command output (in list content) or success state
+       # (in scalar context), or runs the specified data handler.

 
 

-       my ($error_handler, @cmdline) = @_;
+       my ($error_handler, $data_handler, @cmdline) = @_;

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


@@ -187,7 +201,12 @@ sub safe_git (&@) {
 
                chomp;
 
 
                chomp;
 

-               push @lines, $_;
+               if (! defined $data_handler) {
+                       push @lines, $_;
+               }
+               else {
+                       last unless $data_handler->($_);
+               }

        }
 
        close $OUT;
        }
 
        close $OUT;


@@ -197,10 +216,25 @@ sub safe_git (&@) {
        return wantarray ? @lines : ($? == 0);
 }
 # Convenient wrappers.
        return wantarray ? @lines : ($? == 0);
 }
 # Convenient wrappers.

-sub run_or_die ($@) { safe_git(\&error, @_) }
-sub run_or_cry ($@) { safe_git(sub { warn @_ },  @_) }
-sub run_or_non ($@) { safe_git(undef,            @_) }
+sub run_or_die ($@) { safe_git(\&error, undef, @_) }
+sub run_or_cry ($@) { safe_git(sub { warn @_ }, undef, @_) }
+sub run_or_non ($@) { safe_git(undef, undef, @_) }
+
+sub ensure_committer {
+       if (! length $ENV{GIT_AUTHOR_NAME} || ! length $ENV{GIT_COMMITTER_NAME}) {
+               my $name = join('', run_or_non("git", "config", "user.name"));
+               if (! length $name) {
+                       run_or_die("git", "config", "user.name", "IkiWiki");
+               }
+       }

 
 

+       if (! length $ENV{GIT_AUTHOR_EMAIL} || ! length $ENV{GIT_COMMITTER_EMAIL}) {
+               my $email = join('', run_or_non("git", "config", "user.email"));
+               if (! length $email) {
+                       run_or_die("git", "config", "user.email", "ikiwiki.info");
+               }
+       }
+}

 
 sub merge_past ($$$) {
        # Unlike with Subversion, Git cannot make a 'svn merge -rN:M file'.
 
 sub merge_past ($$$) {
        # Unlike with Subversion, Git cannot make a 'svn merge -rN:M file'.


@@ -239,6 +273,8 @@ sub merge_past ($$$) {
        my @undo;      # undo stack for cleanup in case of an error
        my $conflict;  # file content with conflict markers
 
        my @undo;      # undo stack for cleanup in case of an error
        my $conflict;  # file content with conflict markers
 

+       ensure_committer();
+

        eval {
                # Hide local changes from Git by renaming the modified file.
                # Relative paths must be converted to absolute for renaming.
        eval {
                # Hide local changes from Git by renaming the modified file.
                # Relative paths must be converted to absolute for renaming.


@@ -296,8 +332,6 @@ sub merge_past ($$$) {
        return $conflict;
 }
 
        return $conflict;
 }
 

-{
-my $prefix;

 sub decode_git_file ($) {
        my $file=shift;
 
 sub decode_git_file ($) {
        my $file=shift;
 


@@ -319,7 +353,6 @@ sub decode_git_file ($) {
 
        return decode("utf8", $file);
 }
 
        return decode("utf8", $file);
 }

-}

 
 sub parse_diff_tree ($) {
        # Parse the raw diff tree chunk and return the info hash.
 
 sub parse_diff_tree ($) {
        # Parse the raw diff tree chunk and return the info hash.


@@ -327,8 +360,8 @@ sub parse_diff_tree ($) {
        my $dt_ref = shift;
 
        # End of stream?
        my $dt_ref = shift;
 
        # End of stream?

-       return if !defined @{ $dt_ref } ||
-                 !defined @{ $dt_ref }[0] || !length @{ $dt_ref }[0];
+       return if ! @{ $dt_ref } ||
+                 !defined $dt_ref->[0] || !length $dt_ref->[0];

 
        my %ci;
        # Header line.
 
        my %ci;
        # Header line.


@@ -392,6 +425,16 @@ sub parse_diff_tree ($) {
        }
        shift @{ $dt_ref } if $dt_ref->[0] =~ /^$/;
 
        }
        shift @{ $dt_ref } if $dt_ref->[0] =~ /^$/;
 

+       $ci{details} = [parse_changed_files($dt_ref)];
+
+       return \%ci;
+}
+
+sub parse_changed_files {
+       my $dt_ref = shift;
+
+       my @files;
+

        # Modified files.
        while (my $line = shift @{ $dt_ref }) {
                if ($line =~ m{^
        # Modified files.
        while (my $line = shift @{ $dt_ref }) {
                if ($line =~ m{^


@@ -409,7 +452,7 @@ sub parse_diff_tree ($) {
                        my $status = shift(@tmp);
 
                        if (length $file) {
                        my $status = shift(@tmp);
 
                        if (length $file) {

-                               push @{ $ci{'details'} }, {
+                               push @files, {

                                        'file'      => decode_git_file($file),
                                        'sha1_from' => $sha1_from[0],
                                        'sha1_to'   => $sha1_to,
                                        'file'      => decode_git_file($file),
                                        'sha1_from' => $sha1_from[0],
                                        'sha1_to'   => $sha1_to,


@@ -423,7 +466,7 @@ sub parse_diff_tree ($) {
                last;
        }
 
                last;
        }
 

-       return \%ci;
+       return @files;

 }
 
 sub git_commit_info ($;$) {
 }
 
 sub git_commit_info ($;$) {


@@ -436,7 +479,7 @@ sub git_commit_info ($;$) {
 
        my @raw_lines = run_or_die('git', 'log', @opts,
                '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c',
 
        my @raw_lines = run_or_die('git', 'log', @opts,
                '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c',

-               '-r', $sha1, '--', '.');
+               '-r', $sha1, '--no-renames', '--', '.');

 
        my @ci;
        while (my $parsed = parse_diff_tree(\@raw_lines)) {
 
        my @ci;
        while (my $parsed = parse_diff_tree(\@raw_lines)) {


@@ -448,25 +491,70 @@ sub git_commit_info ($;$) {
        return wantarray ? @ci : $ci[0];
 }
 
        return wantarray ? @ci : $ci[0];
 }
 

-sub git_sha1 (;$) {
-       # Return head sha1sum (of given file).
-       my $file = shift || q{--};
+sub rcs_find_changes ($) {
+       my $oldrev=shift;

 
 

+       # Note that git log will sometimes show files being added that
+       # don't exist. Particularly, git merge -s ours can result in a
+       # merge commit where some files were not really added.
+       # This is why the code below verifies that the files really
+       # exist.
+       my @raw_lines = run_or_die('git', 'log',
+               '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c',
+               '--no-renames', , '--reverse',
+               '-r', "$oldrev..HEAD", '--', '.');
+
+       # Due to --reverse, we see changes in chronological order.
+       my %changed;
+       my %deleted;
+       my $nullsha = 0 x 40;
+       my $newrev=$oldrev;
+       while (my $ci = parse_diff_tree(\@raw_lines)) {
+               $newrev=$ci->{sha1};
+               foreach my $i (@{$ci->{details}}) {
+                       my $file=$i->{file};
+                       if ($i->{sha1_to} eq $nullsha) {
+                               if (! -e "$config{srcdir}/$file") {
+                                       delete $changed{$file};
+                                       $deleted{$file}=1;
+                               }
+                       }
+                       else {
+                               if (-e "$config{srcdir}/$file") {
+                                       delete $deleted{$file};
+                                       $changed{$file}=1;
+                               }
+                       }
+               }
+       }
+
+       return (\%changed, \%deleted, $newrev);
+}
+
+sub git_sha1_file ($) {
+       my $file=shift;
+       git_sha1("--", $file);
+}
+
+sub git_sha1 (@) {

        # Ignore error since a non-existing file might be given.
        my ($sha1) = run_or_non('git', 'rev-list', '--max-count=1', 'HEAD',
        # Ignore error since a non-existing file might be given.
        my ($sha1) = run_or_non('git', 'rev-list', '--max-count=1', 'HEAD',

-               '--', $file);
-       if ($sha1) {
+               '--', @_);
+       if (defined $sha1) {

                ($sha1) = $sha1 =~ m/($sha1_pattern)/; # sha1 is untainted now
        }
                ($sha1) = $sha1 =~ m/($sha1_pattern)/; # sha1 is untainted now
        }

-       else {
-               debug("Empty sha1sum for '$file'.");
-       }
-       return defined $sha1 ? $sha1 : q{};
+       return defined $sha1 ? $sha1 : '';
+}
+
+sub rcs_get_current_rev () {
+       git_sha1();

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

+       ensure_committer();
+

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


@@ -477,7 +565,7 @@ sub rcs_prepedit ($) {
        # This will be later used in rcs_commit if a merge is required.
        my ($file) = @_;
 
        # This will be later used in rcs_commit if a merge is required.
        my ($file) = @_;
 

-       return git_sha1($file);
+       return git_sha1_file($file);

 }
 
 sub rcs_commit (@) {
 }
 
 sub rcs_commit (@) {


@@ -488,8 +576,11 @@ sub rcs_commit (@) {
 
        # Check to see if the page has been changed by someone else since
        # rcs_prepedit was called.
 
        # Check to see if the page has been changed by someone else since
        # rcs_prepedit was called.

-       my $cur    = git_sha1($params{file});
-       my ($prev) = $params{token} =~ /^($sha1_pattern)$/; # untaint
+       my $cur    = git_sha1_file($params{file});
+       my $prev;
+       if (defined $params{token}) {
+               ($prev) = $params{token} =~ /^($sha1_pattern)$/; # untaint
+       }

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


@@ -519,27 +610,41 @@ sub rcs_commit_helper (@) {
                elsif (defined $params{session}->remote_addr()) {
                        $u=$params{session}->remote_addr();
                }
                elsif (defined $params{session}->remote_addr()) {
                        $u=$params{session}->remote_addr();
                }

-               if (defined $u) {
+               if (length $u) {

                        $u=encode_utf8($u);
                        $ENV{GIT_AUTHOR_NAME}=$u;
                }
                        $u=encode_utf8($u);
                        $ENV{GIT_AUTHOR_NAME}=$u;
                }

+               else {
+                       $u = 'anonymous';
+               }

                if (defined $params{session}->param("nickname")) {
                        $u=encode_utf8($params{session}->param("nickname"));
                        $u=~s/\s+/_/g;
                        $u=~s/[^-_0-9[:alnum:]]+//g;
                }
                if (defined $params{session}->param("nickname")) {
                        $u=encode_utf8($params{session}->param("nickname"));
                        $u=~s/\s+/_/g;
                        $u=~s/[^-_0-9[:alnum:]]+//g;
                }

-               if (defined $u) {
+               if (length $u) {

                        $ENV{GIT_AUTHOR_EMAIL}="$u\@web";
                }
                        $ENV{GIT_AUTHOR_EMAIL}="$u\@web";
                }

+               else {
+                       $ENV{GIT_AUTHOR_EMAIL}='anonymous@web';
+               }

        }
 
        }
 

+       ensure_committer();
+

        $params{message} = IkiWiki::possibly_foolish_untaint($params{message});
        my @opts;
        if ($params{message} !~ /\S/) {
                # Force git to allow empty commit messages.
                # (If this version of git supports it.)
                my ($version)=`git --version` =~ /git version (.*)/;
        $params{message} = IkiWiki::possibly_foolish_untaint($params{message});
        my @opts;
        if ($params{message} !~ /\S/) {
                # Force git to allow empty commit messages.
                # (If this version of git supports it.)
                my ($version)=`git --version` =~ /git version (.*)/;

-               if ($version ge "1.5.4") {
+               if ($version ge "1.7.8") {
+                       push @opts, "--allow-empty-message", "--no-edit";
+               }
+               if ($version ge "1.7.2") {
+                       push @opts, "--allow-empty-message";
+               }
+               elsif ($version ge "1.5.4") {

                        push @opts, '--cleanup=verbatim';
                }
                else {
                        push @opts, '--cleanup=verbatim';
                }
                else {


@@ -553,7 +658,7 @@ sub rcs_commit_helper (@) {
        # So we should ignore its exit status (hence run_or_non).
        if (run_or_non('git', 'commit', '-m', $params{message}, '-q', @opts)) {
                if (length $config{gitorigin_branch}) {
        # So we should ignore its exit status (hence run_or_non).
        if (run_or_non('git', 'commit', '-m', $params{message}, '-q', @opts)) {
                if (length $config{gitorigin_branch}) {

-                       run_or_cry('git', 'push', $config{gitorigin_branch});
+                       run_or_cry('git', 'push', $config{gitorigin_branch}, $config{gitmaster_branch});

                }
        }
        
                }
        }
        


@@ -566,7 +671,9 @@ sub rcs_add ($) {
 
        my ($file) = @_;
 
 
        my ($file) = @_;
 

-       run_or_cry('git', 'add', $file);
+       ensure_committer();
+
+       run_or_cry('git', 'add', '--', $file);

 }
 
 sub rcs_remove ($) {
 }
 
 sub rcs_remove ($) {


@@ -574,13 +681,17 @@ sub rcs_remove ($) {
 
        my ($file) = @_;
 
 
        my ($file) = @_;
 

-       run_or_cry('git', 'rm', '-f', $file);
+       ensure_committer();
+
+       run_or_cry('git', 'rm', '-f', '--', $file);

 }
 
 sub rcs_rename ($$) {
        my ($src, $dest) = @_;
 
 }
 
 sub rcs_rename ($$) {
        my ($src, $dest) = @_;
 

-       run_or_cry('git', 'mv', '-f', $src, $dest);
+       ensure_committer();
+
+       run_or_cry('git', 'mv', '-f', '--', $src, $dest);

 }
 
 sub rcs_recentchanges ($) {
 }
 
 sub rcs_recentchanges ($) {


@@ -604,9 +715,12 @@ sub rcs_recentchanges ($) {
                my @pages;
                foreach my $detail (@{ $ci->{'details'} }) {
                        my $file = $detail->{'file'};
                my @pages;
                foreach my $detail (@{ $ci->{'details'} }) {
                        my $file = $detail->{'file'};

+                       my $efile = join('/',
+                               map { uri_escape_utf8($_) } split('/', $file)
+                       );

 
                        my $diffurl = defined $config{'diffurl'} ? $config{'diffurl'} : "";
 
                        my $diffurl = defined $config{'diffurl'} ? $config{'diffurl'} : "";

-                       $diffurl =~ s/\[\[file\]\]/$file/go;
+                       $diffurl =~ s/\[\[file\]\]/$efile/go;

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


@@ -663,15 +777,19 @@ sub rcs_recentchanges ($) {
        return @rets;
 }
 
        return @rets;
 }
 

-sub rcs_diff ($) {
+sub rcs_diff ($;$) {

        my $rev=shift;
        my $rev=shift;

+       my $maxlines=shift;

        my ($sha1) = $rev =~ /^($sha1_pattern)$/; # untaint
        my @lines;
        my ($sha1) = $rev =~ /^($sha1_pattern)$/; # untaint
        my @lines;

-       foreach my $line (run_or_non("git", "show", $sha1)) {
-               if (@lines || $line=~/^diff --git/) {
-                       push @lines, $line."\n";
-               }
-       }
+       my $addlines=sub {
+               my $line=shift;
+               return if defined $maxlines && @lines == $maxlines;
+               push @lines, $line."\n"
+                       if (@lines || $line=~/^diff --git/);
+               return 1;
+       };
+       safe_git(undef, $addlines, "git", "show", $sha1);

        if (wantarray) {
                return @lines;
        }
        if (wantarray) {
                return @lines;
        }


@@ -752,6 +870,7 @@ sub git_find_root {
 }
 
 sub git_parse_changes {
 }
 
 sub git_parse_changes {

+       my $reverted = shift;

        my @changes = @_;
 
        my ($subdir, $rootdir) = git_find_root();
        my @changes = @_;
 
        my ($subdir, $rootdir) = git_find_root();


@@ -772,11 +891,11 @@ sub git_parse_changes {
                                $mode=$detail->{'mode_to'};
                        }
                        elsif ($detail->{'status'} =~ /^[AM]+\d*$/) {
                                $mode=$detail->{'mode_to'};
                        }
                        elsif ($detail->{'status'} =~ /^[AM]+\d*$/) {

-                               $action="add";
+                               $action= $reverted ? "remove" : "add";

                                $mode=$detail->{'mode_to'};
                        }
                        elsif ($detail->{'status'} =~ /^[DAM]+\d*/) {
                                $mode=$detail->{'mode_to'};
                        }
                        elsif ($detail->{'status'} =~ /^[DAM]+\d*/) {

-                               $action="remove";
+                               $action= $reverted ? "add" : "remove";

                                $mode=$detail->{'mode_from'};
                        }
                        else {
                                $mode=$detail->{'mode_from'};
                        }
                        else {


@@ -834,9 +953,9 @@ sub rcs_receive () {
                # (Also, if a subdir is involved, we don't want to chdir to
                # it and only see changes in it.)
                # The pre-receive hook already puts us in the right place.
                # (Also, if a subdir is involved, we don't want to chdir to
                # it and only see changes in it.)
                # The pre-receive hook already puts us in the right place.

-               $git_dir=".";
-               push @rets, git_parse_changes(git_commit_info($oldrev."..".$newrev));
-               $git_dir=undef;
+               in_git_dir(".", sub {
+                       push @rets, git_parse_changes(0, git_commit_info($oldrev."..".$newrev));
+               });

        }
 
        return reverse @rets;
        }
 
        return reverse @rets;


@@ -846,24 +965,89 @@ sub rcs_preprevert ($) {
        my $rev=shift;
        my ($sha1) = $rev =~ /^($sha1_pattern)$/; # untaint
 
        my $rev=shift;
        my ($sha1) = $rev =~ /^($sha1_pattern)$/; # untaint
 

+       my @undo;      # undo stack for cleanup in case of an error
+
+       ensure_committer();
+

        # Examine changes from root of git repo, not from any subdir,
        # in order to see all changes.
        my ($subdir, $rootdir) = git_find_root();
        # Examine changes from root of git repo, not from any subdir,
        # in order to see all changes.
        my ($subdir, $rootdir) = git_find_root();

-       $git_dir=$rootdir;
-       my @commits=git_commit_info($sha1, 1);
-       $git_dir=undef;
+       return in_git_dir($rootdir, sub {
+               my @commits=git_commit_info($sha1, 1);
+       
+               if (! @commits) {
+                       error "unknown commit"; # just in case
+               }

 
 

-       if (! @commits) {
-               error "unknown commit"; # just in case
-       }
+               # git revert will fail on merge commits. Add a nice message.
+               if (exists $commits[0]->{parents} &&
+                   @{$commits[0]->{parents}} > 1) {
+                       error gettext("you are not allowed to revert a merge");
+               }

 
 

-       # git revert will fail on merge commits. Add a nice message.
-       if (exists $commits[0]->{parents} &&
-           @{$commits[0]->{parents}} > 1) {
-               error gettext("you are not allowed to revert a merge");
-       }
+               # Due to the presence of rename-detection, we cannot actually
+               # see what will happen in a revert without trying it.
+               # But we can guess, which is enough to rule out most changes
+               # that we won't allow reverting.
+               git_parse_changes(1, @commits);
+
+               my $failure;
+               my @ret;
+               # If it looks OK, do it for real, on a branch.
+               eval {
+                       IkiWiki::disable_commit_hook();
+                       push @undo, sub {
+                               IkiWiki::enable_commit_hook();
+                       };
+                       my $branch = "ikiwiki_revert_${sha1}"; # supposed to be unique
+
+                       push @undo, sub {
+                               run_or_cry('git', 'branch', '-D', $branch) if $failure;
+                       };
+                       if (run_or_non('git', 'rev-parse', '--quiet', '--verify', $branch)) {
+                               run_or_non('git', 'branch', '-D', $branch);
+                       }
+                       run_or_die('git', 'branch', $branch, $config{gitmaster_branch});
+
+                       push @undo, sub {
+                               if (!run_or_cry('git', 'checkout', '--quiet', $config{gitmaster_branch})) {
+                                       run_or_cry('git', 'checkout','-f', '--quiet', $config{gitmaster_branch});
+                               }
+                       };
+                       run_or_die('git', 'checkout', '--quiet', $branch);
+
+                       run_or_die('git', 'revert', '--no-commit', $sha1);
+                       run_or_non('git', 'commit', '-m', "revert $sha1", '-a');
+
+                       # Re-switch to master.
+                       run_or_die('git', 'checkout', '--quiet', $config{gitmaster_branch});

 
 

-       return git_parse_changes(@commits);
+                       my @raw_lines;
+                       @raw_lines = run_or_die('git', 'diff', '--pretty=raw',
+                               '--raw', '--abbrev=40', '--always', '--no-renames',
+                               "ikiwiki_revert_${sha1}..");
+
+                       my $ci = {
+                               details => [parse_changed_files(\@raw_lines)],
+                       };
+
+                       @ret = git_parse_changes(0, $ci);
+               };
+               $failure = $@;
+
+               # Process undo stack (in reverse order).  By policy cleanup
+               # actions should normally print a warning on failure.
+               while (my $handle = pop @undo) {
+                       $handle->();
+               }
+
+               if ($failure) {
+                       my $message = sprintf(gettext("Failed to revert commit %s"), $sha1);
+                       error("$message\n$failure\n");
+               }
+
+               return @ret;
+       });

 }
 
 sub rcs_revert ($) {
 }
 
 sub rcs_revert ($) {


@@ -871,11 +1055,13 @@ sub rcs_revert ($) {
        my $rev = shift;
        my ($sha1) = $rev =~ /^($sha1_pattern)$/; # untaint
 
        my $rev = shift;
        my ($sha1) = $rev =~ /^($sha1_pattern)$/; # untaint
 

-       if (run_or_non('git', 'revert', '--no-commit', $sha1)) {
+       ensure_committer();
+
+       if (run_or_non('git', 'merge', '--ff-only', "ikiwiki_revert_$sha1")) {

                return undef;
        }
        else {
                return undef;
        }
        else {

-               run_or_die('git', 'reset', '--hard');
+               run_or_non('git', 'branch', '-D', "ikiwiki_revert_$sha1");

                return sprintf(gettext("Failed to revert commit %s"), $sha1);
        }
 }
                return sprintf(gettext("Failed to revert commit %s"), $sha1);
        }
 }