gitweb: Fix bug in "blobdiff" view for split (e.g. file to symlink) patches

git_patchset_body needs patch generated with --full-index option to
detect split patches, meaning two patches which corresponds to single
difftree (raw diff) entry.  An example of such situation is changing
type (mode) of a file, e.g. from plain file to symbolic link.

Add, in git_blobdiff, --full-index option to patch generating git diff
invocation, for the 'html' format output ("blobdiff" view).

"blobdiff_plain" still uses shortened sha1 in the extended git diff
header "index <hash>..<hash>[ <mode>]" line.

Noticed-by: Martin Koegler <mkoegler@auto.tuwien.ac.at>
Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -3934,7 +3934,8 @@ sub git_blobdiff {
 
 		# open patch output
 		open $fd, "-|", git_cmd(), "diff-tree", '-r', @diff_opts,
-			'-p', $hash_parent_base, $hash_base,
+			'-p', ($format eq 'html' ? "--full-index" : ()),
+			$hash_parent_base, $hash_base,
 			"--", (defined $file_parent ? $file_parent : ()), $file_name
 			or die_error(undef, "Open git-diff-tree failed");
 	}
@@ -3969,7 +3970,8 @@ sub git_blobdiff {
 		}
 
 		# open patch output
-		open $fd, "-|", git_cmd(), "diff", '-p', @diff_opts,
+		open $fd, "-|", git_cmd(), "diff", @diff_opts,
+			'-p', ($format eq 'html' ? "--full-index" : ()),
 			$hash_parent, $hash, "--"
 			or die_error(undef, "Open git-diff failed");
 	} else  {