Merge branch 'gs/commit-graph-progress'

* gs/commit-graph-progress:
  commit-graph: add --[no-]progress to write and verify
diff --git a/Documentation/git-commit-graph.txt b/Documentation/git-commit-graph.txt
index eb5e786..8c708a7 100644
--- a/Documentation/git-commit-graph.txt
+++ b/Documentation/git-commit-graph.txt
@@ -10,8 +10,8 @@
 --------
 [verse]
 'git commit-graph read' [--object-dir <dir>]
-'git commit-graph verify' [--object-dir <dir>] [--shallow]
-'git commit-graph write' <options> [--object-dir <dir>]
+'git commit-graph verify' [--object-dir <dir>] [--shallow] [--[no-]progress]
+'git commit-graph write' <options> [--object-dir <dir>] [--[no-]progress]
 
 
 DESCRIPTION
@@ -29,6 +29,9 @@
 	commit-graph file is expected to be in the `<dir>/info` directory and
 	the packfiles are expected to be in `<dir>/pack`.
 
+--[no-]progress::
+	Turn progress on/off explicitly. If neither is specified, progress is
+	shown if standard error is connected to a terminal.
 
 COMMANDS
 --------
diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index 052696f..a6c500d 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -10,13 +10,13 @@
 static char const * const builtin_commit_graph_usage[] = {
 	N_("git commit-graph [--object-dir <objdir>]"),
 	N_("git commit-graph read [--object-dir <objdir>]"),
-	N_("git commit-graph verify [--object-dir <objdir>] [--shallow]"),
-	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits] <split options>"),
+	N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]"),
+	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits] [--[no-]progress] <split options>"),
 	NULL
 };
 
 static const char * const builtin_commit_graph_verify_usage[] = {
-	N_("git commit-graph verify [--object-dir <objdir>] [--shallow]"),
+	N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]"),
 	NULL
 };
 
@@ -26,7 +26,7 @@
 };
 
 static const char * const builtin_commit_graph_write_usage[] = {
-	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits] <split options>"),
+	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits] [--[no-]progress] <split options>"),
 	NULL
 };
 
@@ -38,6 +38,7 @@
 	int append;
 	int split;
 	int shallow;
+	int progress;
 } opts;
 
 static int graph_verify(int argc, const char **argv)
@@ -55,9 +56,11 @@
 			   N_("The object directory to store the graph")),
 		OPT_BOOL(0, "shallow", &opts.shallow,
 			 N_("if the commit-graph is split, only verify the tip file")),
+		OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
 		OPT_END(),
 	};
 
+	opts.progress = isatty(2);
 	argc = parse_options(argc, argv, NULL,
 			     builtin_commit_graph_verify_options,
 			     builtin_commit_graph_verify_usage, 0);
@@ -66,6 +69,8 @@
 		opts.obj_dir = get_object_directory();
 	if (opts.shallow)
 		flags |= COMMIT_GRAPH_VERIFY_SHALLOW;
+	if (opts.progress)
+		flags |= COMMIT_GRAPH_WRITE_PROGRESS;
 
 	graph_name = get_commit_graph_filename(opts.obj_dir);
 	open_ok = open_commit_graph(graph_name, &fd, &st);
@@ -154,7 +159,7 @@
 	struct string_list *commit_hex = NULL;
 	struct string_list lines;
 	int result = 0;
-	enum commit_graph_write_flags flags = COMMIT_GRAPH_WRITE_PROGRESS;
+	enum commit_graph_write_flags flags = 0;
 
 	static struct option builtin_commit_graph_write_options[] = {
 		OPT_STRING(0, "object-dir", &opts.obj_dir,
@@ -168,6 +173,7 @@
 			N_("start walk at commits listed by stdin")),
 		OPT_BOOL(0, "append", &opts.append,
 			N_("include all commits already in the commit-graph file")),
+		OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
 		OPT_BOOL(0, "split", &opts.split,
 			N_("allow writing an incremental commit-graph file")),
 		OPT_INTEGER(0, "max-commits", &split_opts.max_commits,
@@ -179,6 +185,7 @@
 		OPT_END(),
 	};
 
+	opts.progress = isatty(2);
 	split_opts.size_multiple = 2;
 	split_opts.max_commits = 0;
 	split_opts.expire_time = 0;
@@ -195,6 +202,8 @@
 		flags |= COMMIT_GRAPH_WRITE_APPEND;
 	if (opts.split)
 		flags |= COMMIT_GRAPH_WRITE_SPLIT;
+	if (opts.progress)
+		flags |= COMMIT_GRAPH_WRITE_PROGRESS;
 
 	read_replace_refs = 0;
 
diff --git a/commit-graph.c b/commit-graph.c
index 19cb1fe..c3ba79f 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1994,8 +1994,10 @@
 	if (verify_commit_graph_error & ~VERIFY_COMMIT_GRAPH_ERROR_HASH)
 		return verify_commit_graph_error;
 
-	progress = start_progress(_("Verifying commits in commit graph"),
-				  g->num_commits);
+	if (flags & COMMIT_GRAPH_WRITE_PROGRESS)
+		progress = start_progress(_("Verifying commits in commit graph"),
+					g->num_commits);
+
 	for (i = 0; i < g->num_commits; i++) {
 		struct commit *graph_commit, *odb_commit;
 		struct commit_list *graph_parents, *odb_parents;
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index ab3eccf..df3fed3 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -124,6 +124,42 @@
 	git repack
 '
 
+test_expect_success 'commit-graph write progress off for redirected stderr' '
+	cd "$TRASH_DIRECTORY/full" &&
+	git commit-graph write 2>err &&
+	test_line_count = 0 err
+'
+
+test_expect_success 'commit-graph write force progress on for stderr' '
+	cd "$TRASH_DIRECTORY/full" &&
+	git commit-graph write --progress 2>err &&
+	test_file_not_empty err
+'
+
+test_expect_success 'commit-graph write with the --no-progress option' '
+	cd "$TRASH_DIRECTORY/full" &&
+	git commit-graph write --no-progress 2>err &&
+	test_line_count = 0 err
+'
+
+test_expect_success 'commit-graph verify progress off for redirected stderr' '
+	cd "$TRASH_DIRECTORY/full" &&
+	git commit-graph verify 2>err &&
+	test_line_count = 0 err
+'
+
+test_expect_success 'commit-graph verify force progress on for stderr' '
+	cd "$TRASH_DIRECTORY/full" &&
+	git commit-graph verify --progress 2>err &&
+	test_file_not_empty err
+'
+
+test_expect_success 'commit-graph verify with the --no-progress option' '
+	cd "$TRASH_DIRECTORY/full" &&
+	git commit-graph verify --no-progress 2>err &&
+	test_line_count = 0 err
+'
+
 # Current graph structure:
 #
 #   __M3___
diff --git a/t/t5324-split-commit-graph.sh b/t/t5324-split-commit-graph.sh
index e2c3953..115aabd 100755
--- a/t/t5324-split-commit-graph.sh
+++ b/t/t5324-split-commit-graph.sh
@@ -320,7 +320,7 @@
 	git merge commits/3 commits/4 &&
 	git branch merge/octopus &&
 	git commit-graph write --reachable --split &&
-	git commit-graph verify 2>err &&
+	git commit-graph verify --progress 2>err &&
 	test_line_count = 3 err &&
 	test_i18ngrep ! warning err &&
 	test_line_count = 3 $graphdir/commit-graph-chain