pack-bitmap-write.c: don't return without stop_progress()

Fix a bug that's been here since 7cc8f97 (pack-objects: implement
bitmap writing, 2013-12-21), we did not call stop_progress() if we
reached the early exit in this function.

We could call stop_progress() before we return, but better yet is to
defer calling start_progress() until we need it. For now this only
matters in practice because we'd previously omit the "region_leave"
for the progress trace2 event.

Suggested-by: SZEDER Gábor <[email protected]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

pack-bitmap-write.c

@@ -544,15 +544,15 @@ void bitmap_writer_select_commits(struct commit **indexed_commits,
 
 	QSORT(indexed_commits, indexed_commits_nr, date_compare);
 
-	if (writer.show_progress)
-		writer.progress = start_progress("Selecting bitmap commits", 0);
-
 	if (indexed_commits_nr < 100) {
 		for (i = 0; i < indexed_commits_nr; ++i)
 			push_bitmapped_commit(indexed_commits[i]);
 		return;
 	}
 
+	if (writer.show_progress)
+		writer.progress = start_progress("Selecting bitmap commits", 0);
+
 	for (;;) {
 		struct commit *chosen = NULL;