commit-graph write: add itermediate progress

Add progress output to sections of code between "Annotating[...]" and
"Computing[...]generation numbers". This can collectively take 5-10
seconds on a large enough repository.

On a test repository with I have with ~7 million commits and ~50
million objects we'll now emit:

    $ ~/g/git/git --exec-path=$HOME/g/git commit-graph write
    Finding commits for commit graph among packed objects: 100% (124763727/124763727), done.
    Loading known commits in commit graph: 100% (18989461/18989461), done.
    Expanding reachable commits in commit graph: 100% (18989507/18989461), done.
    Clearing commit marks in commit graph: 100% (18989507/18989507), done.
    Counting distinct commits in commit graph: 100% (18989507/18989507), done.
    Finding extra edges in commit graph: 100% (18989507/18989507), done.
    Computing commit graph generation numbers: 100% (7250302/7250302), done.
    Writing out commit graph in 4 passes: 100% (29001208/29001208), done.

Whereas on a medium-sized repository such as linux.git these new
progress bars won't have time to kick in and as before and we'll still
emit output like:

    $ ~/g/git/git --exec-path=$HOME/g/git commit-graph write
    Finding commits for commit graph among packed objects: 100% (6529159/6529159), done.
    Expanding reachable commits in commit graph: 815990, done.
    Computing commit graph generation numbers: 100% (815983/815983), done.
    Writing out commit graph in 4 passes: 100% (3263932/3263932), done.

The "Counting distinct commits in commit graph" phase will spend most
of its time paused at "0/*" as we QSORT(...) the list. That's not
optimal, but at least we don't seem to be stalling anymore most of the
time.

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

1 files changed, 13 insertions, 0 deletions

diff --git a/commit-graph.c b/commit-graph.c
index d4a7280fa1..889cdefc49 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -895,12 +895,19 @@ void write_commit_graph(const char *obj_dir,
 
 	close_reachable(&oids, report_progress);
 
+	if (report_progress)
+		progress = start_delayed_progress(
+			_("Counting distinct commits in commit graph"),
+			oids.nr);
+	display_progress(progress, 0); /* TODO: Measure QSORT() progress */
 	QSORT(oids.list, oids.nr, commit_compare);
 	count_distinct = 1;
 	for (i = 1; i < oids.nr; i++) {
+		display_progress(progress, i + 1);
 		if (!oideq(&oids.list[i - 1], &oids.list[i]))
 			count_distinct++;
 	}
+	stop_progress(&progress);
 
 	if (count_distinct >= GRAPH_PARENT_MISSING)
 		die(_("the commit graph format cannot write %d commits"), count_distinct);
@@ -910,8 +917,13 @@ void write_commit_graph(const char *obj_dir,
 	ALLOC_ARRAY(commits.list, commits.alloc);
 
 	num_extra_edges = 0;
+	if (report_progress)
+		progress = start_delayed_progress(
+			_("Finding extra edges in commit graph"),
+			oids.nr);
 	for (i = 0; i < oids.nr; i++) {
 		int num_parents = 0;
+		display_progress(progress, i + 1);
 		if (i > 0 && oideq(&oids.list[i - 1], &oids.list[i]))
 			continue;
 
@@ -928,6 +940,7 @@ void write_commit_graph(const char *obj_dir,
 		commits.nr++;
 	}
 	num_chunks = num_extra_edges ? 4 : 3;
+	stop_progress(&progress);
 
 	if (commits.nr >= GRAPH_PARENT_MISSING)
 		die(_("too many commits to write graph"));