commit-graph write: add "Writing out" progress output

Add progress output to be shown when we're writing out the
commit-graph, this adds to the output already added in 7b0f229222
("commit-graph write: add progress output", 2018-09-17).

As noted in that commit most of the progress output isn't displayed on
small repositories, but before this change we'd noticeably hang for
2-3 seconds at the end on medium sized repositories such as linux.git.

Now we'll instead show output like this, and reduce the
human-observable times at which we're not producing progress output:

    $ ~/g/git/git --exec-path=$HOME/g/git -C ~/g/2015-04-03-1M-git commit-graph write
    Finding commits for commit graph: 13064614, done.
    Expanding reachable commits in commit graph: 1000447, done.
    Computing commit graph generation numbers: 100% (1000447/1000447), done.
    Writing out commit graph: 100% (3001341/3001341), done.

This "Writing out" number is 3x or 4x the number of commits, depending
on the graph we're processing. A later change will make this explicit
to the user.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit-graph.c

@@ -430,7 +430,9 @@ struct tree *get_commit_tree_in_graph(struct repository *r, const struct commit
 
 static void write_graph_chunk_fanout(struct hashfile *f,
 				     struct commit **commits,
-				     int nr_commits)
+				     int nr_commits,
+				     struct progress *progress,
+				     uint64_t *progress_cnt)
 {
 	int i, count = 0;
 	struct commit **list = commits;
@@ -444,6 +446,7 @@ static void write_graph_chunk_fanout(struct hashfile *f,
 		while (count < nr_commits) {
 			if ((*list)->object.oid.hash[0] != i)
 				break;
+			display_progress(progress, ++*progress_cnt);
 			count++;
 			list++;
 		}
@@ -453,12 +456,16 @@ static void write_graph_chunk_fanout(struct hashfile *f,
 }
 
 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
-				   struct commit **commits, int nr_commits)
+				   struct commit **commits, int nr_commits,
+				   struct progress *progress,
+				   uint64_t *progress_cnt)
 {
 	struct commit **list = commits;
 	int count;
-	for (count = 0; count < nr_commits; count++, list++)
+	for (count = 0; count < nr_commits; count++, list++) {
+		display_progress(progress, ++*progress_cnt);
 		hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
+	}
 }
 
 static const unsigned char *commit_to_sha1(size_t index, void *table)
@@ -468,7 +475,9 @@ static const unsigned char *commit_to_sha1(size_t index, void *table)
 }
 
 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
-				   struct commit **commits, int nr_commits)
+				   struct commit **commits, int nr_commits,
+				   struct progress *progress,
+				   uint64_t *progress_cnt)
 {
 	struct commit **list = commits;
 	struct commit **last = commits + nr_commits;
@@ -478,6 +487,7 @@ static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 		struct commit_list *parent;
 		int edge_value;
 		uint32_t packedDate[2];
+		display_progress(progress, ++*progress_cnt);
 
 		parse_commit(*list);
 		hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
@@ -539,7 +549,9 @@ static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 
 static void write_graph_chunk_extra_edges(struct hashfile *f,
 					  struct commit **commits,
-					  int nr_commits)
+					  int nr_commits,
+					  struct progress *progress,
+					  uint64_t *progress_cnt)
 {
 	struct commit **list = commits;
 	struct commit **last = commits + nr_commits;
@@ -547,6 +559,9 @@ static void write_graph_chunk_extra_edges(struct hashfile *f,
 
 	while (list < last) {
 		int num_parents = 0;
+
+		display_progress(progress, ++*progress_cnt);
+
 		for (parent = (*list)->parents; num_parents < 3 && parent;
 		     parent = parent->next)
 			num_parents++;
@@ -768,6 +783,7 @@ void write_commit_graph(const char *obj_dir,
 	int num_extra_edges;
 	struct commit_list *parent;
 	struct progress *progress = NULL;
+	uint64_t progress_cnt = 0;
 
 	if (!commit_graph_compatible(the_repository))
 		return;
@@ -943,11 +959,16 @@ void write_commit_graph(const char *obj_dir,
 		hashwrite(f, chunk_write, 12);
 	}
 
-	write_graph_chunk_fanout(f, commits.list, commits.nr);
-	write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
-	write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
+	if (report_progress)
+		progress = start_delayed_progress(
+			_("Writing out commit graph"),
+			num_chunks * commits.nr);
+	write_graph_chunk_fanout(f, commits.list, commits.nr, progress, &progress_cnt);
+	write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr, progress, &progress_cnt);
+	write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr, progress, &progress_cnt);
 	if (num_extra_edges)
-		write_graph_chunk_extra_edges(f, commits.list, commits.nr);
+		write_graph_chunk_extra_edges(f, commits.list, commits.nr, progress, &progress_cnt);
+	stop_progress(&progress);
 
 	close_commit_graph(the_repository);
 	finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);