submodule add: always initialize .git/config entry

When "git submodule add $path" is run to add a subdirectory $path to the
superproject, and $path is already the top of the working tree of the
submodule repository, the command created submodule.$path.url entry in the
configuration file in the superproject. However, when adding a repository
$URL that is outside the respository of the superproject to $path that
does not exist (yet) with "git submodule add $URL $path", the command
forgot to set it up.

The user is expressing the interest in the submodule and wants to keep a
checkout, the "submodule add" command should consistently set up the
submodule.$path.url entry in either case.

As a result "git submodule init" can't simply skip the initialization of
those submodules for which it finds an url entry in the git./config
anymore. That lead to problems when adding a submodule (which now sets the
url), add the "update" setting to .gitmodules and expect init to copy that
into .git/config like it is done in t7406. So change init to only then
copy the "url" and "update" entries when they don't exist yet in the
.git/config and do nothing otherwise.
Signed-off-by: NJens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -231,7 +231,6 @@ cmd_add()
 			url="$repo"
 			;;
 		esac
-		git config submodule."$path".url "$url"
 	else
 
 		module_clone "$path" "$realrepo" "$reference" || exit
@@ -245,6 +244,7 @@ cmd_add()
 			esac
 		) || die "Unable to checkout submodule '$path'"
 	fi
+	git config submodule."$path".url "$url"
 
 	git add $force "$path" ||
 	die "Failed to add submodule '$path'"
@@ -340,25 +340,26 @@ cmd_init()
 	do
 		# Skip already registered paths
 		name=$(module_name "$path") || exit
-		url=$(git config submodule."$name".url)
-		test -z "$url" || continue
-
-		url=$(git config -f .gitmodules submodule."$name".url)
-		test -z "$url" &&
-		die "No url found for submodule path '$path' in .gitmodules"
-
-		# Possibly a url relative to parent
-		case "$url" in
-		./*|../*)
-			url=$(resolve_relative_url "$url") || exit
-			;;
-		esac
-
-		git config submodule."$name".url "$url" ||
-		die "Failed to register url for submodule path '$path'"
+		if test -z "$(git config "submodule.$name.url")"
+		then
+			url=$(git config -f .gitmodules submodule."$name".url)
+			test -z "$url" &&
+			die "No url found for submodule path '$path' in .gitmodules"
+
+			# Possibly a url relative to parent
+			case "$url" in
+			./*|../*)
+				url=$(resolve_relative_url "$url") || exit
+				;;
+			esac
+			git config submodule."$name".url "$url" ||
+			die "Failed to register url for submodule path '$path'"
+		fi
 
+		# Copy "update" setting when it is not set yet
 		upd="$(git config -f .gitmodules submodule."$name".update)"
 		test -z "$upd" ||
+		test -n "$(git config submodule."$name".update)" ||
 		git config submodule."$name".update "$upd" ||
 		die "Failed to register update mode for submodule path '$path'"