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[ikiwiki] / doc / todo / Attempt_to_extend_Mercurial_backend_support.mdwn

Using the Mercurial backend, the lack of `rcs_commit_staged` is noticed frequently. I couldn't find any tries to update `mercurial.pm`, so not letting lack of Mercurial AND Perl knowledge bring me down, I copy-pasted from `git.pm` to mimic its behaviour from a Mercurial perspective. I hope it can be a foundation for development by those more proficient in ikiwiki's inner workings. I have doubts that I personally will be able to revise it more, based on my Perl skills.

I've tested it briefly. `ikiwiki-calendar` and posting of comments now works with automatic commits, i.e. the `rcs_commit_staged` function works in those cases. Under my current setup, I don't know where else to expect it to work. I would be flabberghasted if there wasn't any problems with it, though.

Diff follows, for anyone to annotate. Code is also available at [my hg-repo](http://510x.se/hg/program/ikiwiki/file/e741fcfd800f/Plugin/mercurial.pm).

        diff -r 20c61288d7bd Plugin/mercurial.pm
        --- a/Plugin/mercurial.pm       Fri Jul 15 02:55:12 2011 +0200
        +++ b/Plugin/mercurial.pm       Fri Jul 15 03:29:10 2011 +0200
        @@ -7,6 +7,8 @@
         use Encode;
         use open qw{:utf8 :std};
         
        +my $hg_dir=undef;
        +
         sub import {
                hook(type => "checkconfig", id => "mercurial", call => \&checkconfig);
                hook(type => "getsetup", id => "mercurial", call => \&getsetup);

A corresponding variable is declared for git. It is unused as of yet for Mercurial, but when more advanced merge features become available for `mercurial.pm`, I think it will come into play.

        @@ -69,6 +71,62 @@
                        },
         }
         
        +sub safe_hg (&@) {
        +       # 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 $pid = open my $OUT, "-|";
        +
        +       error("Cannot fork: $!") if !defined $pid;
        +
        +       if (!$pid) {
        +               # In child.
        +               # hg commands want to be in wc.
        +               if (! defined $hg_dir) {
        +                       chdir $config{srcdir}
        +                           or error("cannot chdir to $config{srcdir}: $!");
        +               }
        +               else {
        +                       chdir $hg_dir
        +                           or error("cannot chdir to $hg_dir: $!");
        +               }
        +               exec @cmdline or error("Cannot exec '@cmdline': $!");
        +       }
        +       # In parent.
        +
        +       # hg output is probably utf-8 encoded, but may contain
        +       # other encodings or invalidly encoded stuff. So do not rely
        +       # on the normal utf-8 IO layer, decode it by hand.
        +       binmode($OUT);
        +
        +       my @lines;
        +       while (<$OUT>) {
        +               $_=decode_utf8($_, 0);
        +
        +               chomp;
        +
        +               if (! defined $data_handler) {
        +                       push @lines, $_;
        +               }
        +               else {
        +                       last unless $data_handler->($_);
        +               }
        +       }
        +
        +       close $OUT;
        +
        +       $error_handler->("'@cmdline' failed: $!") if $? && $error_handler;
        +
        +       return wantarray ? @lines : ($? == 0);
        +}
        +# Convenient wrappers.
        +sub run_or_die ($@) { safe_hg(\&error, undef, @_) }
        +sub run_or_cry ($@) { safe_hg(sub { warn @_ }, undef, @_) }
        +sub run_or_non ($@) { safe_hg(undef, undef, @_) }
        +
         sub mercurial_log ($) {
                my $out = shift;
                my @infos;
        @@ -116,10 +174,7 @@
         }
         
         sub rcs_update () {
        -       my @cmdline = ("hg", "-q", "-R", "$config{srcdir}", "update");
        -       if (system(@cmdline) != 0) {
        -               warn "'@cmdline' failed: $!";
        -       }
        +       run_or_cry('hg', '-q', 'update');
         }
         
         sub rcs_prepedit ($) {

With the `run_or_{die,cry,non}()` functions defined as in `git.pm`, some old Mercurial functions can be rewritten more compactly.

        @@ -129,6 +184,14 @@
         sub rcs_commit (@) {
                my %params=@_;
         
        +       return rcs_commit_helper(@_);
        +}
        +
        +sub rcs_commit_helper (@) {
        +       my %params=@_;
        +
        +       my %env=%ENV;
        +
                my $user="Anonymous";
                if (defined $params{session}) {
                        if (defined $params{session}->param("name")) {

Here comes the `rcs_commit{,_staged}` part. It is modeled on a `rcs_commit_helper` function, as in `git.pm`.

Some old `mercurial.pm` logic concerning commiter name is kept instead of transplanting the more elaborate logic from `git.pm`. Maybe it is better to "steal" that as well.

        @@ -143,43 +206,45 @@
                        $params{message} = "no message given";
                }
         
        -       my @cmdline = ("hg", "-q", "-R", $config{srcdir}, "commit", 
        -                      "-m", IkiWiki::possibly_foolish_untaint($params{message}),
        -                      "-u", IkiWiki::possibly_foolish_untaint($user));
        -       if (system(@cmdline) != 0) {
        -               warn "'@cmdline' failed: $!";
        +       $params{message} = IkiWiki::possibly_foolish_untaint($params{message});
        +
        +       my @opts;
        +       
        +       if (exists $params{file}) {
        +               push @opts, '--', $params{file};
                }
        -
        +       # hg commit returns non-zero if nothing really changed.
        +       # So we should ignore its exit status (hence run_or_non).
        +       run_or_non('hg', 'commit', '-m', $params{message}, '-q', @opts);
        +       
        +       %ENV=%env;
                return undef; # success
         }
         
         sub rcs_commit_staged (@) {
                # Commits all staged changes. Changes can be staged using rcs_add,
                # rcs_remove, and rcs_rename.
        -       my %params=@_;
        -       
        -       error("rcs_commit_staged not implemented for mercurial"); # TODO
        +       return rcs_commit_helper(@_);
         }
         
         sub rcs_add ($) {
                my ($file) = @_;
         
        -       my @cmdline = ("hg", "-q", "-R", "$config{srcdir}", "add", "$config{srcdir}/$file");
        -       if (system(@cmdline) != 0) {
        -               warn "'@cmdline' failed: $!";
        -       }
        +       run_or_cry('hg', 'add', $file);
         }
         
         sub rcs_remove ($) {
        +       # Remove file from archive.
        +
                my ($file) = @_;
         
        -       error("rcs_remove not implemented for mercurial"); # TODO
        +       run_or_cry('hg', 'remove', '-f', $file);
         }
         
         sub rcs_rename ($$) {
                my ($src, $dest) = @_;
         
        -       error("rcs_rename not implemented for mercurial"); # TODO
        +       run_or_cry('hg', 'rename', '-f', $src, $dest);
         }
         
         sub rcs_recentchanges ($) {