status: add status.aheadbehind setting

The --[no-]ahead-behind option was introduced in fd9b544a
(status: add --[no-]ahead-behind to status and commit for V2
format, 2018-01-09). This is a necessary change of behavior
in repos where the remote tracking branches can move very
quickly ahead of the local branches. However, users need to
remember to provide the command-line argument every time.

Add a new "status.aheadBehind" config setting to change the
default behavior of all git status formats.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/status.txt

@@ -12,6 +12,11 @@ status.branch::
 	Set to true to enable --branch by default in linkgit:git-status[1].
 	The option --no-branch takes precedence over this variable.
 
+status.aheadBehind::
+	Set to true to enable `--ahead-behind` and false to enable
+	`--no-ahead-behind` by default in linkgit:git-status[1] for
+	non-porcelain status formats.  Defaults to true.
+
 status.displayCommentPrefix::
 	If set to true, linkgit:git-status[1] will insert a comment
 	prefix before each output line (starting with

builtin/commit.c

@@ -1078,9 +1078,11 @@ static const char *read_commit_message(const char *name)
 static struct status_deferred_config {
 	enum wt_status_format status_format;
 	int show_branch;
+	enum ahead_behind_flags ahead_behind;
 } status_deferred_config = {
 	STATUS_FORMAT_UNSPECIFIED,
-	-1 /* unspecified */
+	-1, /* unspecified */
+	AHEAD_BEHIND_UNSPECIFIED,
 };
 
 static void finalize_deferred_config(struct wt_status *s)
@@ -1107,6 +1109,15 @@ static void finalize_deferred_config(struct wt_status *s)
 	if (s->show_branch < 0)
 		s->show_branch = 0;
 
+	/*
+	 * If the user did not give a "--[no]-ahead-behind" command
+	 * line argument, then we inherit the a/b config setting.
+	 * If is not set, then we inherit _FULL for backwards
+	 * compatibility.
+	 */
+	if (s->ahead_behind_flags == AHEAD_BEHIND_UNSPECIFIED)
+		s->ahead_behind_flags = status_deferred_config.ahead_behind;
+
 	if (s->ahead_behind_flags == AHEAD_BEHIND_UNSPECIFIED)
 		s->ahead_behind_flags = AHEAD_BEHIND_FULL;
 }
@@ -1246,6 +1257,10 @@ static int git_status_config(const char *k, const char *v, void *cb)
 		status_deferred_config.show_branch = git_config_bool(k, v);
 		return 0;
 	}
+	if (!strcmp(k, "status.aheadbehind")) {
+		status_deferred_config.ahead_behind = git_config_bool(k, v);
+		return 0;
+	}
 	if (!strcmp(k, "status.showstash")) {
 		s->show_stash = git_config_bool(k, v);
 		return 0;

t/t6040-tracking-info.sh

@@ -159,6 +159,19 @@ test_expect_success 'status -s -b --no-ahead-behind (diverged from upstream)' '
 	test_i18ncmp expect actual
 '
 
+cat >expect <<\EOF
+## b1...origin/master [different]
+EOF
+
+test_expect_success 'status.aheadbehind=false status -s -b (diverged from upstream)' '
+	(
+		cd test &&
+		git checkout b1 >/dev/null &&
+		git -c status.aheadbehind=false status -s -b | head -1
+	) >actual &&
+	test_i18ncmp expect actual
+'
+
 cat >expect <<\EOF
 On branch b1
 Your branch and 'origin/master' have diverged,
@@ -174,6 +187,15 @@ test_expect_success 'status --long --branch' '
 	test_i18ncmp expect actual
 '
 
+test_expect_success 'status --long --branch' '
+	(
+		cd test &&
+		git checkout b1 >/dev/null &&
+		git -c status.aheadbehind=true status --long -b | head -3
+	) >actual &&
+	test_i18ncmp expect actual
+'
+
 cat >expect <<\EOF
 On branch b1
 Your branch and 'origin/master' refer to different commits.
@@ -188,6 +210,15 @@ test_expect_success 'status --long --branch --no-ahead-behind' '
 	test_i18ncmp expect actual
 '
 
+test_expect_success 'status.aheadbehind=false status --long --branch' '
+	(
+		cd test &&
+		git checkout b1 >/dev/null &&
+		git -c status.aheadbehind=false status --long -b | head -2
+	) >actual &&
+	test_i18ncmp expect actual
+'
+
 cat >expect <<\EOF
 ## b5...brokenbase [gone]
 EOF

t/t7064-wtstatus-pv2.sh

@@ -436,6 +436,10 @@ test_expect_success 'verify --[no-]ahead-behind with V2 format' '
 		git status --no-ahead-behind --porcelain=v2 --branch --untracked-files=all >actual &&
 		test_cmp expect actual &&
 
+		# Confirmat that "status.aheadbehind" works on V2 format.
+		git -c status.aheadbehind=false status --porcelain=v2 --branch --untracked-files=all >actual &&
+		test_cmp expect actual &&
+
 		# Confirm --ahead-behind reports traditional branch.ab with 1/0.
 		cat >expect <<-EOF &&
 		# branch.oid $HUF