@@ -3082,6 +3082,11 @@ status.submoduleSummary::
 	submodule summary' command, which shows a similar output but does
 	not honor these settings.
 
+status.noaheadbehind::
+	Do not compute ahead/behind counts for a branch relative to its
+	upstream branch.  This can be used to avoid a possibly very
+	expensive computation on extremely large repositories.
+
 stash.showPatch::
 	If this is set to true, the `git stash show` command without an
 	option will show the stash entry in patch form.  Defaults to false.

@@ -111,6 +111,13 @@ configuration variable documented in linkgit:git-config[1].
 	without options are equivalent to 'always' and 'never'
 	respectively.
 
+--no-ahead-behind::
+	Do not compute ahead/behind counts for the current branch relative
+	to the upstream branch.  This can be used to avoid a possibly very
+	expensive computation on extremely large repositories.
++
+	In porcelain V2 format, the 'branch.ab' line will not be present.
+
 <pathspec>...::
 	See the 'pathspec' entry in linkgit:gitglossary[7].
 

@@ -253,6 +260,9 @@ information about the current branch.
 					     the commit is present.
     ------------------------------------------------------------
 
+If `--no-ahead-behind` is given or 'status.noaheadbehind' is set, the
+'branch.ab' line will not be present.
+
 ### Changed Tracked Entries
 
 Following the headers, a series of lines are printed for tracked

@@ -1335,6 +1335,10 @@ static int git_status_config(const char *k, const char *v, void *cb)
 			return error(_("Invalid untracked files mode '%s'"), v);
 		return 0;
 	}
+	if (!strcmp(k, "status.noaheadbehind")) {
+		s->no_ahead_behind = git_config_bool(k, v);
+		return 0;
+	}
 	return git_diff_ui_config(k, v, NULL);
 }
 

@@ -1369,6 +1373,8 @@ int cmd_status(int argc, const char **argv, const char *prefix)
 		  N_("ignore changes to submodules, optional when: all, dirty, untracked. (Default: all)"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t)"all" },
 		OPT_COLUMN(0, "column", &s.colopts, N_("list untracked files in columns")),
+		OPT_BOOL(0, "no-ahead-behind", &s.no_ahead_behind,
+			 N_("omit branch ahead/behind counts")),
 		OPT_END(),
 	};
 

@@ -390,6 +390,29 @@ test_expect_success 'verify upstream fields in branch header' '
 	)
 '
 
+test_expect_success 'verify --no-ahead-behind omits branch.ab' '
+	git checkout master &&
+	test_when_finished "rm -rf sub_repo" &&
+	git clone . sub_repo &&
+	(
+		## Confirm local master tracks remote master.
+		cd sub_repo &&
+		HUF=$(git rev-parse HEAD) &&
+
+		cat >expect <<-EOF &&
+		# branch.oid $HUF
+		# branch.head master
+		# branch.upstream origin/master
+		EOF
+
+		git status --no-ahead-behind --porcelain=v2 --branch --untracked-files=all >actual &&
+		test_cmp expect actual &&
+
+		git -c status.noaheadbehind=true status --porcelain=v2 --branch --untracked-files=all >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_expect_success 'create and add submodule, submodule appears clean (A. S...)' '
 	git checkout master &&
 	git clone . sub_repo &&

@@ -1889,6 +1889,8 @@ static void wt_porcelain_print(struct wt_status *s)
  *                 <eol> ::= NUL when -z,
  *                           LF when NOT -z.
  *
+ * When 'status.noaheadbehind' is true or '--no-ahead-behind'
+ * is given on the command line, the 'branch.ab' line is omitted.
  */
 static void wt_porcelain_v2_print_tracking(struct wt_status *s)
 {

@@ -1928,7 +1930,14 @@ static void wt_porcelain_v2_print_tracking(struct wt_status *s)
 		/* Lookup stats on the upstream tracking branch, if set. */
 		branch = branch_get(branch_name);
 		base = NULL;
-		ab_info = (stat_tracking_info(branch, &nr_ahead, &nr_behind, &base) == 0);
+
+		if (s->no_ahead_behind) {
+			base = branch_get_upstream(branch, NULL);
+			ab_info = 0;
+		} else {
+			ab_info = (stat_tracking_info(branch, &nr_ahead, &nr_behind, &base) == 0);
+		}
+
 		if (base) {
 			base = shorten_unambiguous_ref(base, 0);
 			fprintf(s->fp, "# branch.upstream %s%c", base, eol);

@@ -80,6 +80,7 @@ struct wt_status {
 	int show_branch;
 	int show_stash;
 	int hints;
+	int no_ahead_behind;
 
 	enum wt_status_format status_format;
 	unsigned char sha1_commit[GIT_MAX_RAWSZ]; /* when not Initial */