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[ikiwiki] / doc / todo / darcs.mdwn

Here's Thomas Schwinge unfinished darcs support for ikiwiki.

(Finishing this has been suggested as a [[soc]] project.)

> I haven't been working on this for months and also won't in the near
> future.  Feel free to use what I have done so
> far and bring it into an usable state!  Also, feel free to contact me
>  if there are questions.

-- [Thomas Schwinge](mailto:tschwinge@gnu.org)

[[!toggle text="show"]]
[[!toggleable text="""
        # Support for the darcs rcs, <URL:http://darcs.net/>.
        # Copyright (C) 2006  Thomas Schwinge <tschwinge@gnu.org>
        #
        # This program is free software; you can redistribute it and/or modify it
        # under the terms of the GNU General Public License as published by the
        # Free Software Foundation; either version 2 of the License, or (at your
        # option) any later version.
        #
        # This program is distributed in the hope that it will be useful, but
        # WITHOUT ANY WARRANTY; without even the implied warranty of
        # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        # General Public License for more details.
        #
        # You should have received a copy of the GNU General Public License along
        # with this program; if not, write to the Free Software Foundation, Inc.,
        # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
        
        
        # We're guaranteed to be the only instance of ikiwiki running at a given
        # time.  It is essential that only ikiwiki is working on a particular
        # repository.  That means one instance of ikiwiki and it also means that
        # you must not `darcs push' into this repository, as this might create
        # race conditions, as I understand it.
        
        
        use warnings;
        use strict;
        use IkiWiki;
        
        package IkiWiki;
        
        
        # Which darcs executable to use.
        my $darcs = ($ENV{DARCS} or 'darcs');
        
        
        # Internal functions.
        
        sub darcs_info ($$$) {
            my $field = shift;
            my $repodir = shift;
            my $file = shift; # Relative to the repodir.
        
            my $child = open(DARCS_CHANGES, "-|");
            if (! $child) {
                exec($darcs, 'changes', '--repo=' . $repodir, '--xml-output', $file) or
                    error('failed to run `darcs changes\'');
            }
        
            # Brute force for now.  :-/
            while (<DARCS_CHANGES>) {
                last if /^<\/created_as>$/;
            }
            ($_) = <DARCS_CHANGES> =~ /$field=\'([^\']+)/;
            $field eq 'hash' and s/\.gz//; # Strip away the `.gz' from `hash'es.
        
            close(DARCS_CHANGES) or error('`darcs changes\' exited ' . $?);
        
            return $_;
        }
        
        
        # Exported functions.
        
        sub rcs_update () {
            # Not needed.
        }
        
        sub rcs_prepedit ($) {
            # Prepares to edit a file under revision control.  Returns a token that
            # must be passed to rcs_commit() when the file is to be commited.  For us,
            # this token the hash value of the latest patch that modifies the file,
            # i.e. something like its current revision.  If the file is not yet added
            # to the repository, we return TODO: the empty string.
        
            my $file = shift; # Relative to the repodir.
        
            my $hash = darcs_info('hash', $config{srcdir}, $file);
            return defined $hash ? $hash : "";
        }
        
        sub rcs_commit ($$$) {
            # Commit the page.  Returns `undef' on success and a version of the page
            # with conflict markers on failure.
        
            my $file = shift; # Relative to the repodir.
            my $message = shift;
            my $rcstoken = shift;
        
            # Compute if the ``revision'' of $file changed.
            my $changed = darcs_info('hash', $config{srcdir}, $file) ne $rcstoken;
        
            # Yes, the following is a bit convoluted.
            if ($changed) {
                # TODO.  Invent a better, non-conflicting name.
                rename("$config{srcdir}/$file", "$config{srcdir}/$file.save") or
                    error("failed to rename $file to $file.save: $!");
        
                # Roll the repository back to $rcstoken.
        
                # TODO.  Can we be sure that no changes are lost?  I think that
                # we can, if we make sure that the `darcs push' below will always
                # succeed.
        
                # We need to revert everything as `darcs obliterate' might choke
                # otherwise.
                # TODO: `yes | ...' needed?  Doesn't seem so.
                system($darcs, "revert", "--repodir=" . $config{srcdir}, "--all") and
                    error("`darcs revert' failed");
                # Remove all patches starting at $rcstoken.
                # TODO.  Something like `yes | darcs obliterate ...' seems to be needed.
                system($darcs, "obliterate", "--quiet", "--repodir" . $config{srcdir},
                       "--match", "hash " . $rcstoken) and
                           error("`darcs obliterate' failed");
                # Restore the $rcstoken one.
                system($darcs, "pull", "--quiet", "--repodir=" . $config{srcdir},
                       "--match", "hash " . $rcstoken, "--all") and
                           error("`darcs pull' failed");
        
                # We're back at $rcstoken.  Re-install the modified file.
                rename("$config{srcdir}/$file.save", "$config{srcdir}/$file") or
                    error("failed to rename $file.save to $file: $!");
            }
        
            # Record the changes.
            # TODO: What if $message is empty?
            writefile("$file.log", $config{srcdir}, $message);
            system($darcs, 'record', '--repodir=' . $config{srcdir}, '--all',
                   '--logfile=' . "$config{srcdir}/$file.log",
                   '--author=' . 'web commit <web-hurd@gnu.org>', $file) and
                       error('`darcs record\' failed');
        
            # Update the repository by pulling from the default repository, which is
            # master repository.
            system($darcs, "pull", "--quiet", "--repodir=" . $config{srcdir},
                   "--all") and error("`darcs pull' failed\n");
        
            # If this updating yields any conflicts, we'll record them now to resolve
            # them.  If nothing is recorded, there are no conflicts.
            $rcstoken = darcs_info('hash', $config{srcdir}, $file);
            # TODO: Use only the first line here, i.e. only the patch name?
            writefile("$file.log", $config{srcdir}, 'resolve conflicts: ' . $message);
            system($darcs, 'record', '--repodir=' . $config{srcdir}, '--all',
                   '--logfile=' . "$config{srcdir}/$file.log",
                   '--author=' . 'web commit <web-hurd@gnu.org>', $file) and
                       error('`darcs record\' failed');
            my $conflicts = darcs_info('hash', $config{srcdir}, $file) ne $rcstoken;
            unlink("$config{srcdir}/$file.log") or
                error("failed to remove `$file.log'");
        
            # Push the changes to the main repository.
            system($darcs, 'push', '--quiet', '--repodir=' . $config{srcdir}, '--all')
                and error('`darcs push\' failed');
            # TODO: darcs send?
        
            if ($conflicts) {
                my $document = readfile("$config{srcdir}/$file");
                # Try to leave everything in a consistent state.
                # TODO: `yes | ...' needed?  Doesn't seem so.
                system($darcs, "revert", "--repodir=" . $config{srcdir}, "--all") and
                    warn("`darcs revert' failed.\n");
                return $document;
            } else {
                return undef;
            }
        }
        
        sub rcs_add ($) {
            my $file = shift; # Relative to the repodir.
        
            # Intermediate directories will be added automagically.
            system($darcs, 'add', '--quiet', '--repodir=' . $config{srcdir},
                   '--boring', $file) and error('`darcs add\' failed');
        }
        
        sub rcs_recentchanges ($) {
            warn('rcs_recentchanges() is not implemented');
            return 'rcs_recentchanges() is not implemented';
        }
        
        sub rcs_notify () {
            warn('rcs_notify() is not implemented');
        }
        
        sub rcs_getctime () {
            warn('rcs_getctime() is not implemented');
        }
        
        1
"""]]

This is my ([bma](bma@bmalee.eu)) darcs.pm - it's messy (my Perl isn't up to much) but seems to work. It uses just one repo, like the mercurial plugin (unlike the above version, which AIUI uses two).

`rcs_commit()` uses backticks instead of `system()`, to prevent darcs' output being sent to the browser and mucking with the HTTP headers (`darcs record` has no --quiet option). And `rcs_recentchanges()` uses regexes rather than parsing darcs' XML output.

[[!toggle text="show" id="bma"]]
[[!toggleable id="bma" text="""

        #!/usr/bin/perl
        
        use warnings;
        use strict;
        use IkiWiki;
        use Date::Parse;
        use open qw{:utf8 :std};
        
        package IkiWiki;
        
        sub rcs_update () { #{{{
                # Do nothing - there's nowhere to update *from*.
        } #}}}
        
        sub rcs_prepedit ($) { #{{{
        } #}}}
        
        sub rcs_commit ($$$;$$) { #{{{
                my ($file, $message, $rcstoken, $user, $ipaddr) = @_;
        
                # $user should probably be a name and an email address, by darcs
                # convention.
                if (defined $user) {
                        $user = possibly_foolish_untaint($user);
                }
                elsif (defined $ipaddr) {
                        $user = "Anonymous from $ipaddr";
                }
                else {
                        $user = "Anonymous";
                }
        
                $message = possibly_foolish_untaint($message);
                
                # BUG: this outputs one line of text, and there's not a -q or --quiet
                # option. Redirecting output to /dev/null works, but I still get the
                # HTTP status and location headers displayed in the browser - is that
                # darcs' fault or ikiwiki's?
                # Doing it in backticks *works*, but I'm sure it could be done better.
                my @cmdline = ("darcs", "record", "--repodir", "$config{srcdir}",
                               "-a", "-m", "$message", "--author", "$user", $file);
                `darcs record --repodir "$config{srcdir}" -a -m "$message" --author "$user" $file`; # Return value? Output? Who needs 'em?
                #if (system(@cmdline) != 0) {
                #       warn "'@cmdline' failed: $!";
                #}
        
                return undef; # success
                
        sub rcs_add ($) { # {{{
                my ($file) = @_;
        
                my @cmdline = ("darcs", "add", "--repodir", "$config{srcdir}", "-a", "-q", "$file");
                if (system(@cmdline) != 0) {
                        warn "'@cmdline' failed: $!";
                }
        } #}}}
        
        sub rcs_recentchanges ($) { #{{{
                # TODO: This is horrible code. It doesn't work perfectly, and uses regexes
                # rather than parsing Darcs' XML output.
                my $num=shift;
                my @ret;
                
                return unless -d "$config{srcdir}/_darcs";
        
                my $changelog = `darcs changes --xml --summary --repodir "$config{srcdir}"`;
                $changelog = join("", split(/\s*\n\s*/, $changelog));
                my @changes = split(/<\/patch>.*?<patch/m, $changelog);
        
        
                foreach my $change (@changes) {
                        $change =~ m/hash='(.*?)'/;
                        my $rev = $1;
                        $change =~ m/author='(.*?)'/;
                        my $user = $1."\n";
                        my $committype = "web";
                        if($user =~ m/&lt;/) {
                                # Author fields generated by darcs include an email address: look for the "<".
                                $committype = "darcs";
                                use HTML::Entities;
                                $user = decode_entities $user;
                        }
                        $change =~ m/local_date='(.*?)'/;
                        my $when = $1;
                        $when=time - str2time($when, 'UTC');
                        $change =~ m/<name>(.*?)<\/name>/g;
                        my @message = {line => $1};
                        foreach my $match ($change =~ m/<comment>(.*?)<\/comment>/gm) {
                                push @message, {line => $1};
                        }

                        my @pages;
                        foreach my $match ($change =~ m/<.*?_(file|directory)>(.*?)(<(added|removed)_lines.*\/>)*<\/.*?_(file|directory)>/g) {
                                # My perl-fu is weak. I'm probably going about this all wrong, anyway.
                                push @pages, {page => pagename($match)} if ( -f $config{srcdir}."/".$match || -d $config{srcdir}."/".$match) and not $match =~ m/^$/;
                        }
                        push @ret, { rev => $rev,
                                        user => $user,
                                        committype => $committype,
                                        when => $when,
                                        message => [@message],
                                        pages => [@pages],
                                }
                }
                return @ret;
        } #}}}
        
        sub rcs_notify () { #{{{
                # TODO
        } #}}}
        
        sub rcs_getctime ($) { #{{{
                error gettext("getctime not implemented");
        } #}}}
        
        1



"""]]

---

Well, here's my version too. It only does getctime -- using a real XML parser, instead of regexp ugliness -- and maybe recentchanges, but that may be bitrotted, or maybe I never finished it, as I only need the getctime. As for actual commits, I have previously voiced my opinion, that this should be done by the plugin generating a patch bundle, and forwarding it to darcs in some way (`darcs apply` or even email to another host, possibly moderated), instead of the hacky direct modification of a working copy. It could also be faster to getctime in a batch. Just reading in all the changes the first time they're needed, might not be a big improvement in many cases, but if we got a batch request from ikiwiki, we could keep reaing the changes until all the files in this batch request have been met.  --[[tuomov]]

[[!toggle text="show" id="tuomov"]]
[[!toggleable id="tuomov" text="""
<pre>
#!/usr/bin/perl
# Stubs for no revision control.

use warnings;
use strict;
use IkiWiki;

package IkiWiki;

sub rcs_update () {
}

sub rcs_prepedit ($) {
        return ""
}

sub rcs_commit ($$$) {
        return undef # success
}

sub rcs_add ($) {
}

sub rcs_recentchanges ($) {
        my $num=shift;
        my @ret;
        
        eval q{use Date::Parse};
        eval q{use XML::Simple};
        
        my $repodir=$config{srcdir};
        
        if (-d "$config{srcdir}/_darcs") {
                my $child = open(LOG, "-|");
                if (! $child) {
                        exec("darcs", "changes", "--xml", 
                             "--repodir", "$repodir",
                             "--last", "$num")
                        || error("darcs changes failed to run");
                }
                my $data=<LOG>;
                close LOG;
                
                my $log = XMLin($data, ForceArray => 1);
                
                foreach my $patch ($log->{patch}) {
                        my $date=$patch->{local_date};
                        my $hash=$patch->{hash};
                        my $when=concise(ago(time - str2time($date)));
                        my @pages;
                        
                        my $child = open(SUMMARY, "-|");
                        if (! $child) {
                                exec("darcs", "annotate", "-s", "--xml", 
                                     "--match", "hash: $hash",
                                     "--repodir", "$repodir")
                                || error("darcs annotate failed to run");
                        }
                        my $data=<SUMMARY>;
                        close SUMMARY;
                
                        my $summary = XMLin("<lame>$data</lame>", ForceArray => 1);

                        # TODO: find @pages
                        
                        push @ret, {
                                #rev => $rev,
                                user => $patch->{author},
                                #committype => $committype,
                                when => $when, 
                                #message => [@message],
                                pages => [@pages],
                        }; # if @pages;
                        return @ret if @ret >= $num;
                }
        }
        
        return @ret;
}

sub rcs_notify () {
}

sub rcs_getctime ($) {
        my $file=shift;
        
        eval q{use Date::Parse};
        eval q{use XML::Simple};
        local $/=undef;
        
        # Sigh... doing things the hard way again
        my $repodir=$config{srcdir};
        
        my $filer=substr($file, length($repodir));
        $filer =~ s:^[/]+::;
        
        my $child = open(LOG, "-|");
        if (! $child) {
                exec("darcs", "changes", "--xml", "--reverse",
                     "--repodir", "$repodir", "$filer")
                || error("darcs changes $filer failed to run");
        }
        
        my $data=<LOG>;
        close LOG;
        
        my $log = XMLin($data, ForceArray => 1);
        
        my $datestr=$log->{patch}[0]->{local_date};
        
        if (! defined $datestr) {
                warn "failed to get ctime for $filer";
                return 0;
        }
        
        my $date=str2time($datestr);
        
        debug("found ctime ".localtime($date)." for $file");
        
        return $date;
}

1
</pre>
"""]]

---

I merged the two versions above and made some fixes; it is recording my web edits in darcs and showing a recent changes page.
It is in a [darcs repository](http://joyful.com/darcsweb/darcsweb.cgi?r=ikiwiki-darcs), please send patches. --[[Simon_Michael]]

> I'd like to see at least the following fixed before I commit this: --[[Joey]]
> * Running `darcs record $filename` in backticks is not good (security)
>   The thing to do is to open stdout to /dev/null before execing darcs.
> * Get `rcs_recentchanges_xml` working, parsing xml with regexps does
>   not seem like a maintenance win.
> * `rcs_notify` should be removed, it's no longer used.
> * Some form of conflict handling. Using darcs to attempt to merge
>   the changes is I gusss optional (although every other rcs backend,
>   including svn manages to do this), but it needs to at *least* detect
>   conflicts and return a page with conflict markers for the user to fix
>   the conflict.

I have addressed the recentchanges bit, you can find my hacked up darcs.pm at <http://web.mornfall.net/stuff/web-root/IkiWiki/Rcs/darcs.pm>.

It's got couple of FIXMEs, and a very site-specific filter for recentchanges. Not sure how to do that better though. I will eventually add web commits, probably of my own (and mention it here).

[[!tag patch]]