[PATCH 6] gitweb: Add git_get_{following,preceding}_references functions

[Jakub Narebski <jnareb@gmail.com>]

Adds git_get_following_references function, based on code which was
used in git_commitdiff_plain to generate X-Git-Tag: header,
and companion git_get_preceding_references function.

Both functions return array of all references of given type (as
returned by git_get_references) following/preceding given commit in
array (list) context, and last following/first preceding ref in scalar
context.

Stripping ref (list of refs) of "$type/" (e.g. "tags/") is left to
caller.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
Junio C Hamano wrote:
>>  * "commitdiff_plain" now only generates X-Git-Tag: line only if
>> there is tag pointing to the current commit.
>
> Hmph...
>
>>    ...; besides we are
>>    interested rather in tags _preceding_ the commit, and _heads_
>>    following the commit.
>
> Interesting observation.  When somebody says "feature X was
> introduced in such and such commit", people would want to know (1)
> the point release they are using has the feature -- which means you
> would want to know the earliest tag that comes after the commit, or
> (2) if the branch they are working on already has that
> feature -- which again means if the head follows the commit.  So
> I am not sure when preceding tag is interesting...

Actually, the two following patches adresses this, not this patch...

 gitweb/gitweb.perl |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index d72b19a..2d3776a 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -749,6 +749,58 @@ sub git_get_references {
 	return \%refs;
 }
 
+sub git_get_following_references {
+	my $hash = shift || return undef;
+	my $type = shift;
+	my $base = shift || $hash_base || "HEAD";
+
+	my $refs = git_get_references($type);
+	open my $fd, "-|", $GIT, "rev-list", $base
+		or return undef;
+	my @commits = map { chomp; $_ } <$fd>;
+	close $fd
+		or return undef;
+
+	my @reflist;
+	my $lastref;
+
+	foreach my $commit (@commits) {
+		foreach my $ref (@{$refs->{$commit}}) {
+			$lastref = $ref;
+			push @reflist, $lastref;
+		}
+		if ($commit eq $hash) {
+			last;
+		}
+	}
+
+	return wantarray ? @reflist : $lastref;
+}
+
+sub git_get_preceding_references {
+	my $hash = shift || return undef;
+	my $type = shift;
+
+	my $refs = git_get_references($type);
+	open my $fd, "-|", $GIT, "rev-list", $hash
+		or return undef;
+	my @commits = map { chomp; $_ } <$fd>;
+	close $fd
+		or return undef;
+
+	my @reflist;
+	my $firstref;
+
+	foreach my $commit (@commits) {
+		foreach my $ref (@{$refs->{$commit}}) {
+			$firstref = $ref unless $firstref;
+			push @reflist, $ref;
+		}
+	}
+
+	return wantarray ? @reflist : $firstref;
+}
+
 ## ----------------------------------------------------------------------
 ## parse to hash functions
 
-- 
1.4.1.1