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

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

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

This also fixes a micro-regression in my change of the minimum SHA1
length from 8 to 7, which is that dated tags like
hadoop-20160921-113441-20-g094fb7d would start thinking the "20160921"
part was a commit.

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 whatever 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.
---
 gitweb/gitweb.perl | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 101dbc0..3a52bc7 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;
 }
-- 
2.1.3