Merge branch 'it/log-format-source'

Custom userformat "log --format" learned %S atom that stands for
the tip the traversal reached the commit from, i.e. --source.

* it/log-format-source:
  log: add %S option (like --source) to log --format

builtin/log.c

@@ -203,7 +203,7 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 	    rev->diffopt.filter || rev->diffopt.flags.follow_renames)
 		rev->always_show_header = 0;
 
-	if (source) {
+	if (source || w.source) {
 		init_revision_sources(&revision_sources);
 		rev->sources = &revision_sources;
 	}