builtin/push.c: respect 'submodule.recurse' option

The closest mapping from the boolean 'submodule.recurse' set to "yes"
to the variety of submodule push modes is "on-demand", so implement that.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/push.c

@@ -498,6 +498,10 @@ static int git_push_config(const char *k, const char *v, void *cb)
 		const char *value;
 		if (!git_config_get_value("push.recursesubmodules", &value))
 			recurse_submodules = parse_push_recurse_submodules_arg(k, value);
+	} else if (!strcmp(k, "submodule.recurse")) {
+		int val = git_config_bool(k, v) ?
+			RECURSE_SUBMODULES_ON_DEMAND : RECURSE_SUBMODULES_OFF;
+		recurse_submodules = val;
 	}
 
 	return git_default_config(k, v, NULL);

t/t5531-deep-submodule-push.sh

@@ -126,6 +126,27 @@ test_expect_success 'push succeeds if submodule commit not on remote but using o
 	)
 '
 
+test_expect_success 'push succeeds if submodule commit not on remote but using auto-on-demand via submodule.recurse config' '
+	(
+		cd work/gar/bage &&
+		>recurse-on-demand-from-submodule-recurse-config &&
+		git add recurse-on-demand-from-submodule-recurse-config &&
+		git commit -m "Recurse submodule.recurse from config junk"
+	) &&
+	(
+		cd work &&
+		git add gar/bage &&
+		git commit -m "Recurse submodule.recurse from config for gar/bage" &&
+		git -c submodule.recurse push ../pub.git master &&
+		# Check that the supermodule commit got there
+		git fetch ../pub.git &&
+		git diff --quiet FETCH_HEAD master &&
+		# Check that the submodule commit got there too
+		cd gar/bage &&
+		git diff --quiet origin/master master
+	)
+'
+
 test_expect_success 'push recurse-submodules on command line overrides config' '
 	(
 		cd work/gar/bage &&