t/git-cgi.t: fix race condition

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

diff --git a/IkiWiki/Plugin/git.pm b/IkiWiki/Plugin/git.pm
index cadc69e24d6f1f610bf5a6f1d93e35a20ec966b3..7a6a554952079787f8d5c15b4c4f74159812d1c9 100644 (file)
--- a/IkiWiki/Plugin/git.pm
+++ b/IkiWiki/Plugin/git.pm
@@ -5,11 +5,12 @@ use warnings;
 use strict;
 use IkiWiki;
 use Encode;
 use strict;
 use IkiWiki;
 use Encode;

+use File::Path qw{remove_tree};
+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 +30,8 @@ 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 () {


@@ -151,12 +154,57 @@ sub genwrapper {
        }
 }
 
        }
 }
 

-sub safe_git (&@) {
+my @git_dir_stack;
+my $prefix;
+
+sub in_git_dir ($$) {
+       unshift @git_dir_stack, shift;
+       my @ret=shift->();
+       shift @git_dir_stack;
+       $prefix=undef;
+       return @ret;
+}
+
+# Loosely based on git-new-workdir from git contrib.
+sub create_temp_working_dir ($$) {
+       my $rootdir = shift;
+       my $branch = shift;
+       my $working = "$rootdir/.git/ikiwiki-temp-working";
+       remove_tree($working);
+
+       foreach my $dir ("", ".git") {
+               if (!mkdir("$working/$dir")) {
+                       error("Unable to create $working/$dir: $!");
+               }
+       }
+
+       # Hooks are deliberately not included: we will commit to the temporary
+       # branch that is used in the temporary working tree, and we don't want
+       # to run the post-commit hook there.
+       #
+       # logs/refs is not included because we don't use the reflog.
+       # remotes, rr-cache, svn are similarly excluded.
+       foreach my $link ("config", "refs", "objects", "info", "packed-refs") {
+               if (!symlink("../../$link", "$working/.git/$link")) {
+                       error("Unable to create symlink $working/.git/$link: $!");
+               }
+       }
+
+       open (my $out, '>', "$working/.git/HEAD") or
+               error("failed to write $working.git/HEAD: $!");
+       print $out "ref: refs/heads/$branch\n" or
+               error("failed to write $working.git/HEAD: $!");
+       close $out or
+               error("failed to write $working.git/HEAD: $!");
+       return $working;
+}
+
+sub safe_git {

        # 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.
 
        # 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, $data_handler, @cmdline) = @_;
+       my %params = @_;

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


@@ -165,15 +213,20 @@ sub safe_git (&@) {
        if (!$pid) {
                # In child.
                # Git commands want to be in wc.
        if (!$pid) {
                # In child.
                # Git commands want to be in wc.

-               if (! defined $git_dir) {
+               if (! @git_dir_stack) {

                        chdir $config{srcdir}
                            or error("cannot chdir to $config{srcdir}: $!");
                }
                else {
                        chdir $config{srcdir}
                            or error("cannot chdir to $config{srcdir}: $!");
                }
                else {

-                       chdir $git_dir
-                           or error("cannot chdir to $git_dir: $!");
+                       chdir $git_dir_stack[0]
+                           or error("cannot chdir to $git_dir_stack[0]: $!");
+               }
+
+               if ($params{stdout}) {
+                       open(STDOUT, '>&', $params{stdout}) or error("Cannot reopen stdout: $!");

                }
                }

-               exec @cmdline or error("Cannot exec '@cmdline': $!");
+
+               exec @{$params{cmdline}} or error("Cannot exec '@{$params{cmdline}}': $!");

        }
        # In parent.
 
        }
        # In parent.
 


@@ -188,25 +241,40 @@ sub safe_git (&@) {
 
                chomp;
 
 
                chomp;
 

-               if (! defined $data_handler) {
+               if (! defined $params{data_handler}) {

                        push @lines, $_;
                }
                else {
                        push @lines, $_;
                }
                else {

-                       last unless $data_handler->($_);
+                       last unless $params{data_handler}->($_);

                }
        }
 
        close $OUT;
 
                }
        }
 
        close $OUT;
 

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

 
        return wantarray ? @lines : ($? == 0);
 }
 # Convenient wrappers.
 
        return wantarray ? @lines : ($? == 0);
 }
 # Convenient wrappers.

-sub run_or_die ($@) { safe_git(\&error, undef, @_) }
-sub run_or_cry ($@) { safe_git(sub { warn @_ }, undef, @_) }
-sub run_or_non ($@) { safe_git(undef, undef, @_) }
+sub run_or_die ($@) { safe_git(error_handler => \&error, cmdline => \@_) }
+sub run_or_cry ($@) { safe_git(error_handler => sub { warn @_ }, cmdline => \@_) }
+sub run_or_non ($@) { safe_git(cmdline => \@_) }
+
+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'.


@@ -245,6 +313,8 @@ 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.


@@ -302,8 +372,6 @@ sub merge_past ($$$) {
        return $conflict;
 }
 
        return $conflict;
 }
 

-{
-my $prefix;

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


@@ -325,7 +393,6 @@ 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.


@@ -333,8 +400,8 @@ 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.


@@ -398,6 +465,16 @@ 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{^


@@ -415,7 +492,7 @@ 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,


@@ -429,7 +506,7 @@ sub parse_diff_tree ($) {
                last;
        }
 
                last;
        }
 

-       return \%ci;
+       return @files;

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


@@ -442,7 +519,7 @@ 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)) {


@@ -454,25 +531,70 @@ 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});
        }


@@ -483,7 +605,7 @@ 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 (@) {


@@ -494,8 +616,11 @@ 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);


@@ -525,27 +650,41 @@ 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 {


@@ -559,7 +698,7 @@ 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});

                }
        }
        
                }
        }
        


@@ -572,7 +711,9 @@ 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 ($) {


@@ -580,13 +721,17 @@ 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 ($) {


@@ -610,9 +755,12 @@ 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;


@@ -681,7 +829,11 @@ sub rcs_diff ($;$) {
                        if (@lines || $line=~/^diff --git/);
                return 1;
        };
                        if (@lines || $line=~/^diff --git/);
                return 1;
        };

-       safe_git(undef, $addlines, "git", "show", $sha1);
+       safe_git(
+               error_handler => undef,
+               data_handler => $addlines,
+               cmdline => ["git", "show", $sha1],
+       );

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


@@ -762,6 +914,7 @@ 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();


@@ -782,11 +935,11 @@ 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 {


@@ -810,11 +963,11 @@ sub git_parse_changes {
                                die $@ if $@;
                                my $fh;
                                ($fh, $path)=File::Temp::tempfile(undef, UNLINK => 1);
                                die $@ if $@;
                                my $fh;
                                ($fh, $path)=File::Temp::tempfile(undef, UNLINK => 1);

-                               my $cmd = "cd $git_dir && ".
-                                         "git show $detail->{sha1_to} > '$path'";
-                               if (system($cmd) != 0) {
-                                       error("failed writing temp file '$path'.");
-                               }
+                               safe_git(
+                                       error_handler => sub { error("failed writing temp file '$path': ".shift."."); },
+                                       stdout => $fh,
+                                       cmdline => ['git', 'show', $detail->{sha1_to}],
+                               );

                        }
 
                        push @rets, {
                        }
 
                        push @rets, {


@@ -844,9 +997,9 @@ 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;


@@ -856,24 +1009,83 @@ 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;
+               eval {
+                       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});
+
+                       my $working = create_temp_working_dir($rootdir, $branch);
+
+                       push @undo, sub {
+                               remove_tree($working);
+                       };

 
 

-       return git_parse_changes(@commits);
+                       in_git_dir($working, sub {
+                               run_or_die('git', 'checkout', '--quiet', '--force', $branch);
+                               run_or_die('git', 'revert', '--no-commit', $sha1);
+                               run_or_die('git', 'commit', '-m', "revert $sha1", '-a');
+                       });
+
+                       my @raw_lines;
+                       @raw_lines = run_or_die('git', 'diff', '--pretty=raw',
+                               '--raw', '--abbrev=40', '--always', '--no-renames',
+                               "..${branch}");
+
+                       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 ($) {


@@ -881,11 +1093,13 @@ 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', $sha1)) {
+       ensure_committer();
+
+       if (run_or_non('git', 'cherry-pick', '--no-commit', "ikiwiki_revert_$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);
        }
 }