gpush: add support for gerrit topic names

ui-wise, i considered the alternative of parsing the topic out of the
target ref like a regular push to old versions of gerrit does. however,
given that specifying a target branch is rather uncommon when using
gpush, this seemed pointless.

the topic is persisted (cached) locally, so the purely off-line --list
mode can make use of it.

Change-Id: I032a1f0c3d2b0e84db594e2e162978a2eff66d21
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>

2 files changed, 65 insertions, 7 deletions

diff --git a/bin/git-gpush b/bin/git-gpush
index b467fea..49f256f 100755
--- a/bin/git-gpush
+++ b/bin/git-gpush
@@ -67,6 +67,10 @@ Options:
         Push for specified branch despite the pushed Changes having
         been pushed previously, but only for different branches.
 
+    -t, --topic
+        Specify the Gerrit topic name for the pushed Changes.
+        This setting persists for the series, even when it grows.
+
     -l, --list
         Report all Changes that would be pushed, then quit.
         This is a purely off-line operation.
@@ -139,6 +143,7 @@ EOM
 my $ref_from;
 my $ref_to;
 my $force_branch = 0;
+my $topic;
 my $force = 0;
 my $list_only = 0;
 my $list_online = 0;
@@ -165,6 +170,9 @@ sub parse_arguments(@)
         } elsif ($arg eq "-r" || $arg eq "--remote") {
             fail("--remote needs an argument.\n") if (!@_ || ($_[0] =~ /^-/));
             $remote = shift @_;
+        } elsif ($arg eq "-t" || $arg eq "--topic") {
+            fail("--topic needs an argument.\n") if (!@_ || ($_[0] =~ /^-/));
+            $topic = shift @_;
         } elsif ($arg eq "-b" || $arg eq "--branch") {
             fail("--branch needs an argument.\n") if (!@_ || ($_[0] =~ /^-/));
             $ref_to = shift @_;
@@ -218,7 +226,7 @@ sub parse_arguments(@)
 
     my $push_specific =
             @reviewers || @CCs || $force || $force_branch
-            || defined($remote) || defined($ref_to);
+            || defined($remote) || defined($ref_to) || defined($topic);
 
     if ($list_only) {
         fail("--list/--list-online is incompatible with --quiet/--verbose.\n")
@@ -260,12 +268,14 @@ sub caption_group($)
     my $changes = $$group{changes};
     my $to = $$group{branch};
     my $tos = defined($to) ? " for $to" : "";
+    my $tpc = $$group{topic};
+    my $tpcs = length($tpc) ? ", topic '$tpc'" : "";
     my ($pfx, $rmt) = $list_only
                           ? ("Series of",
                              ($list_online && length($tos)) ? " on '$remote'" : "")
                           : ("Pushing", " to '$remote'");
-    return (sprintf("%s %d Change(s)%s%s:",
-                    $pfx, int(@$changes), $tos, $rmt),
+    return (sprintf("%s %d Change(s)%s%s%s:",
+                    $pfx, int(@$changes), $tos, $rmt, $tpcs),
             $changes);
 }
 
@@ -408,6 +418,20 @@ sub determine_remote_branch($)
     $$group{branch} = $br;
 }
 
+sub determine_topic($)
+{
+    my ($group) = @_;
+
+    my $tpc = $topic;
+    if (!defined($tpc)) {
+        # No topic was specified, so deduce it from the previous push(es).
+        $tpc = aggregate_property($group, 'topic',
+                                  sub { $_[0]->{topic} },
+                                  sub { '  /'.$_[0] });
+    }
+    $$group{topic} = $tpc;
+}
+
 sub finalize_get_changes($)
 {
     my ($changes) = @_;
@@ -516,6 +540,8 @@ sub map_remote_changes($)
         }
         if ($good) {
             $$change{gerrit} = $good;
+            # This overrides the current value, which is just a cache.
+            $$change{topic} = $$good{topic};
         } elsif (@bad && !$force_branch) {
             my @bbr = map { $$_{branch} } @bad;
             $$change{annotation} = '  ['.join(" ", sort @bbr).']';
@@ -727,6 +753,20 @@ sub prepare_meta($)
     $$group{add_rvrs} = [ keys %invite_rvrs ];
     $$group{add_ccs} = [ keys %invite_ccs ];
     $$group{invite_list} = \@invite_list;
+
+    my @topic_list;
+    my $tpc = $$group{topic};
+    if (defined($tpc)) {
+        my $any;
+        foreach my $change (@{$$group{changes}}) {
+            next if ($tpc eq ($$change{topic} // ""));
+            $any = 1;
+            # Can't set topic of unmodified Changes with a push.
+            add_if_unmodified($change, \@topic_list);
+        }
+        $$group{topic} = undef if (!$any);
+    }
+    $$group{topic_list} = \@topic_list;
 }
 
 sub push_changes($)
@@ -736,9 +776,11 @@ sub push_changes($)
     my $from = $$group{changes}[-1];
     my $tip = $$from{local}{id};
     my $to = $$group{branch};
+    my $tpc = $$group{topic};
     my ($rvrs, $ccs) = ($$group{add_rvrs} // [], $$group{add_ccs} // []);
 
     my @push_options;
+    push @push_options, "topic=$tpc" if (defined($tpc));
     push @push_options, map { "r=$_" } @$rvrs;
     push @push_options, map { "cc=$_" } @$ccs;
 
@@ -774,16 +816,27 @@ sub update_unpushed($)
         write_process($pipe, encode_json($json)."\n");
         close_process($pipe);
     }
+
+    my $topic_list = $$group{topic_list};
+    if (@$topic_list) {
+        # TODO: This can be done with the REST API.
+        print "Warning: Cannot set topic on unmodified commits.\n";
+    }
 }
 
 sub update_state($)
 {
     my ($group) = @_;
 
-    my $branch = $$group{branch};
+    my ($branch, $tpc) = ($$group{branch}, $$group{topic});
+    # Setting an empty topic clears the previous topic from the server.
+    $tpc = undef if (defined($tpc) && !length($tpc));
     foreach my $change (@{$$group{changes}}) {
         my $sha1 = $$change{local}{id};
-        $$change{pushed} = $sha1;
+        if (($$change{pushed} // "") ne $sha1) {
+            $$change{pushed} = $sha1;
+            $$change{topic} = $tpc;
+        }
         $$change{tgt} = $branch;
     }
 }
@@ -810,6 +863,9 @@ sub execute_pushing()
     if ($online) {
         check_merges($group);
         map_remote_changes($group);
+    }
+    determine_topic($group);
+    if ($online) {
         classify_changes_online($group);
     } elsif (!$quiet) {
         classify_changes_offline($group);
diff --git a/bin/git_gpush.pm b/bin/git_gpush.pm
index 2997d71..512fa87 100644
--- a/bin/git_gpush.pm
+++ b/bin/git_gpush.pm
@@ -523,6 +523,7 @@ our %gerrit_infos_by_id;
 # - id: Gerrit Change-Id.
 # - src: Local branch name, or "-" if Change is on a detached HEAD.
 # - tgt: Target branch name.
+# - topic: Gerrit topic. Persisted only as a cache.
 # - pushed: SHA1 of the commit this Change was pushed as last time
 #   from this repository.
 
@@ -566,7 +567,7 @@ sub save_state(;$)
 
     print "Saving state".($dry ? " [DRY]" : "")." ...\n" if ($debug);
     my (@lines, @updates);
-    my @fkeys = ('key', 'id', 'src', 'tgt');
+    my @fkeys = ('key', 'id', 'src', 'tgt', 'topic');
     my @rkeys = ('pushed');
     push @lines,
         "next_key $next_key",
@@ -1109,7 +1110,7 @@ sub query_gerrit($;$)
         push @{$gerrit_infos_by_id{$changeid}}, $ginfo;
         my $status = $$review{'status'};
         defined($status) or fail("Huh?! $changeid has no status?\n");
-        my $branch = $$review{'branch'};
+        my ($branch, $topic) = ($$review{'branch'}, $$review{'topic'});
         defined($branch) or fail("Huh?! $changeid has no branch?\n");
         my $pss = $$review{'patchSets'};
         defined($pss) or fail("Huh?! $changeid has no PatchSets?\n");
@@ -1129,6 +1130,7 @@ sub query_gerrit($;$)
         $$ginfo{id} = $changeid;
         $$ginfo{status} = $status;
         $$ginfo{branch} = $branch;
+        $$ginfo{topic} = $topic;
         $$ginfo{revs} = [ grep { $_ } @revs ];  # Drop deleted ones.
         $$ginfo{rev_by_id} = \%rev_map;
         my $rvrs = $$review{'allReviewers'};