submodule: teach set-url subcommand

Currently, in the event that a submodule's upstream URL changes, users
have to manually alter the URL in the .gitmodules file then run
`git submodule sync`. Let's make that process easier.

Teach submodule the set-url subcommand which will automatically change
the `submodule.$name.url` property in the .gitmodules file and then run
`git submodule sync` to complete the process.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-submodule.txt

@@ -16,6 +16,7 @@ SYNOPSIS
 'git submodule' [--quiet] deinit [-f|--force] (--all|[--] <path>...)
 'git submodule' [--quiet] update [<options>] [--] [<path>...]
 'git submodule' [--quiet] set-branch [<options>] [--] <path>
+'git submodule' [--quiet] set-url [--] <path> <newurl>
 'git submodule' [--quiet] summary [<options>] [--] [<path>...]
 'git submodule' [--quiet] foreach [--recursive] <command>
 'git submodule' [--quiet] sync [--recursive] [--] [<path>...]
@@ -180,6 +181,11 @@ set-branch (-d|--default) [--] <path>::
 	`--default` option removes the submodule.<name>.branch configuration
 	key, which causes the tracking branch to default to 'master'.
 
+set-url [--] <path> <newurl>::
+	Sets the URL of the specified submodule to <newurl>. Then, it will
+	automatically synchronize the submodule's new remote URL
+	configuration.
+
 summary [--cached|--files] [(-n|--summary-limit) <n>] [commit] [--] [<path>...]::
 	Show commit summary between the given commit (defaults to HEAD) and
 	working tree/index. For a submodule in question, a series of commits

contrib/completion/git-completion.bash

@@ -2779,7 +2779,7 @@ _git_submodule ()
 {
 	__git_has_doubledash && return
 
-	local subcommands="add status init deinit update set-branch summary foreach sync absorbgitdirs"
+	local subcommands="add status init deinit update set-branch set-url summary foreach sync absorbgitdirs"
 	local subcommand="$(__git_find_on_cmdline "$subcommands")"
 	if [ -z "$subcommand" ]; then
 		case "$cur" in

git-submodule.sh

@@ -12,6 +12,7 @@ USAGE="[--quiet] [--cached]
    or: $dashless [--quiet] deinit [-f|--force] (--all| [--] <path>...)
    or: $dashless [--quiet] update [--init] [--remote] [-N|--no-fetch] [-f|--force] [--checkout|--merge|--rebase] [--[no-]recommend-shallow] [--reference <repository>] [--recursive] [--] [<path>...]
    or: $dashless [--quiet] set-branch (--default|--branch <branch>) [--] <path>
+   or: $dashless [--quiet] set-url [--] <path> <newurl>
    or: $dashless [--quiet] summary [--cached|--files] [--summary-limit <n>] [commit] [--] [<path>...]
    or: $dashless [--quiet] foreach [--recursive] <command>
    or: $dashless [--quiet] sync [--recursive] [--] [<path>...]
@@ -760,6 +761,55 @@ cmd_set_branch() {
 	fi
 }
 
+#
+# Configures a submodule's remote url
+#
+# $@ = requested path, requested url
+#
+cmd_set_url() {
+	while test $# -ne 0
+	do
+		case "$1" in
+		-q|--quiet)
+			GIT_QUIET=1
+			;;
+		--)
+			shift
+			break
+			;;
+		-*)
+			usage
+			;;
+		*)
+			break
+			;;
+		esac
+		shift
+	done
+
+	if test $# -ne 2
+	then
+		usage
+	fi
+
+	# we can't use `git submodule--helper name` here because internally, it
+	# hashes the path so a trailing slash could lead to an unintentional no match
+	name="$(git submodule--helper list "$1" | cut -f2)"
+	if test -z "$name"
+	then
+		exit 1
+	fi
+
+	url="$2"
+	if test -z "$url"
+	then
+		exit 1
+	fi
+
+	git submodule--helper config submodule."$name".url "$url"
+	git submodule--helper sync ${GIT_QUIET:+--quiet} "$name"
+}
+
 #
 # Show commit summary for submodules in index or working tree
 #
@@ -1059,7 +1109,7 @@ cmd_absorbgitdirs()
 while test $# != 0 && test -z "$command"
 do
 	case "$1" in
-	add | foreach | init | deinit | update | set-branch | status | summary | sync | absorbgitdirs)
+	add | foreach | init | deinit | update | set-branch | set-url | status | summary | sync | absorbgitdirs)
 		command=$1
 		;;
 	-q|--quiet)

t/t7420-submodule-set-url.sh

@@ -0,0 +1,55 @@
+#!/bin/sh
+#
+# Copyright (c) 2019 Denton Liu
+#
+
+test_description='Test submodules set-url subcommand
+
+This test verifies that the set-url subcommand of git-submodule is working
+as expected.
+'
+
+TEST_NO_CREATE_REPO=1
+. ./test-lib.sh
+
+test_expect_success 'submodule config cache setup' '
+	mkdir submodule &&
+	(
+		cd submodule &&
+		git init &&
+		echo a >file &&
+		git add file &&
+		git commit -ma
+	) &&
+	mkdir super &&
+	(
+		cd super &&
+		git init &&
+		git submodule add ../submodule &&
+		git commit -m "add submodule"
+	)
+'
+
+test_expect_success 'test submodule set-url' '
+	# add a commit and move the submodule (change the url)
+	(
+		cd submodule &&
+		echo b >>file &&
+		git add file &&
+		git commit -mb
+	) &&
+	mv submodule newsubmodule &&
+
+	git -C newsubmodule show >expect &&
+	(
+		cd super &&
+		test_must_fail git submodule update --remote &&
+		git submodule set-url submodule ../newsubmodule &&
+		grep -F "url = ../newsubmodule" .gitmodules &&
+		git submodule update --remote
+	) &&
+	git -C super/submodule show >actual &&
+	test_cmp expect actual
+'
+
+test_done