Add decorations to commit pages

This adds the tag and branch head decorations to the commit pages.  This is
similar to how commits are displayed in the standard gitweb interface.

Signed-off-by: Justin Waters <justin.waters@timesys.com>

ui-log.h

@@ -3,5 +3,6 @@
 
 extern void cgit_print_log(const char *tip, int ofs, int cnt, char *grep,
 			   char *pattern, char *path, int pager);
+extern void show_commit_decorations(struct commit *commit);
 
 #endif /* UI_LOG_H */