[PATCH v2 3/3] gitweb: Link to "git describe"'d commits in log messages

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Oct 6, 2016, 09:11 UTC
Message-ID: <20161006091135.29590-4-avarab@gmail.com>
In-Reply-To: <20161006091135.29590-1-avarab@gmail.com>

Change the log formatting function to know about "git describe" output such as "v2.8.0-4-g867ad08", in addition to just plain "867ad08".

There are still many valid refnames that we don't link to e.g. v2.10.0-rc1~2^2~1 is also a valid way to refer to v2.8.0-4-g867ad08, but I'm not supporting that with this commit, similarly it's trivially possible to create some refnames like "æ/var-gf6727b0" or which won't be picked up by this regex.

There's surely room for improvement here, but I just wanted to address the very common case of sticking "git describe" output into commit messages without trying to link to all possible refnames, that's going to be a rather futile exercise given that this is free text, and it would be prohibitively expensive to look up whether the references in question exist in our repository.

There was on-list discussion about how we could do better than this patch. Junio suggested to update parse_commits() to call a new "gitweb--helper" command which would pass each of the revision candidates through "rev-parse --verify --quiet". That would cut down on our false positives (e.g. we'll link to "deadbeef"), and also allow us to be more aggressive in selecting candidate revisions.

That may be too expensive to work in practice, or it may not. Investigating that would be a good follow-up to this patch.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 gitweb/gitweb.perl | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 92b5e91..7cf68f0 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -2036,10 +2036,24 @@ sub format_log_line_html {
 	my $line = shift;
 
 	$line = esc_html($line, -nbsp=>1);
-	$line =~ s{\b([0-9a-fA-F]{7,40})\b}{
+	$line =~ s{
+        \b
+        (
+            # The output of "git describe", e.g. v2.10.0-297-gf6727b0
+            # or hadoop-20160921-113441-20-g094fb7d
+            (?<!-) # see strbuf_check_tag_ref(). Tags can't start with -
+            [A-Za-z0-9.-]+
+            (?!\.) # refs can't end with ".", see check_refname_format()
+            -g[0-9a-fA-F]{7,40}
+            |
+            # Just a normal looking Git SHA1
+            [0-9a-fA-F]{7,40}
+        )
+        \b
+    }{
 		$cgi->a({-href => href(action=>"object", hash=>$1),
 					-class => "text"}, $1);
-	}eg;
+	}egx;
 
 	return $line;
 }

-- 
2.9.3