[PATCH 6/6] commit-graph write: add even more progress output

[Ævar Arnfjörð Bjarmason]

Add more progress output to sections of code that can collectively
take 5-10 seconds on a large enough repository. On a test repository
with 7141512 commits (see earlier patches for details) we'll now emit:

    $ ~/g/git/git --exec-path=$HOME/g/git commit-graph write
    Finding commits for commit graph among packed objects: 100% 
(50009986/50009986), done.
    Annotating commit graph: 21564240, done.
    Counting distinct commits in commit graph: 100% (7188080/7188080), done.
    Finding extra edges in commit graph: 100% (7188080/7188080), done.
    Computing commit graph generation numbers: 100% (7143635/7143635), done.
    Writing out commit graph chunks: 21431282, done.

Whereas on a medium-sized repository such as linux.git 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% 
(6365328/6365328), done.
    Annotating commit graph: 2391621, done.
    Computing commit graph generation numbers: 100% (797207/797207), done.
    Writing out commit graph chunks: 2399867, 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.

Signed-off-by: Ævar Arnfjörð Bjarmason <ava...@gmail.com>
---
 commit-graph.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/commit-graph.c b/commit-graph.c
index d0961e89df..2e2eaa24ca 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -893,12 +893,19 @@ 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);
@@ -908,8 +915,13 @@ 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;
 
@@ -926,6 +938,7 @@ 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"));
-- 
2.20.0.rc0.387.gc7a69e6b6c