git-submodule - allow a relative path as the subproject url

This allows a subproject's location to be specified and stored as relative
to the parent project's location (e.g., ./foo, or ../foo). This url is
stored in .gitmodules as given. It is resolved into an absolute url by
appending it to the parent project's url when the information is written
to .git/config (i.e., during submodule add for the originator, and
submodule init for a downstream recipient). This allows cloning of the
project to work "as expected" if the project is hosted on a different
server than when the subprojects were added.

Signed-off-by: Mark Levedahl <mdl123@verizon.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-submodule.txt

@@ -21,6 +21,9 @@ add::
 	repository is cloned at the specified path, added to the
 	changeset and registered in .gitmodules.   If no path is
 	specified, the path is deduced from the repository specification.
+	If the repository url begins with ./ or ../, it is stored as
+	given but resolved as a relative path from the main project's
+	url when cloning.
 
 status::
 	Show the status of the submodules. This will print the SHA-1 of the

git-submodule.sh

@@ -39,6 +39,32 @@ get_repo_base() {
 	) 2>/dev/null
 }
 
+# Resolve relative url by appending to parent's url
+resolve_relative_url ()
+{
+	branch="$(git symbolic-ref HEAD 2>/dev/null)"
+	remote="$(git config branch.${branch#refs/heads/}.remote)"
+	remote="${remote:-origin}"
+	remoteurl="$(git config remote.$remote.url)" ||
+		die "remote ($remote) does not have a url in .git/config"
+	url="$1"
+	while test -n "$url"
+	do
+		case "$url" in
+		../*)
+			url="${url#../}"
+			remoteurl="${remoteurl%/*}"
+			;;
+		./*)
+			url="${url#./}"
+			;;
+		*)
+			break;;
+		esac
+	done
+	echo "$remoteurl/$url"
+}
+
 #
 # Map submodule path to submodule name
 #
@@ -103,11 +129,19 @@ module_add()
 		usage
 	fi
 
-	# Turn the source into an absolute path if
-	# it is local
-	if base=$(get_repo_base "$repo"); then
-		repo="$base"
-	fi
+	case "$repo" in
+	./*|../*)
+		# dereference source url relative to parent's url
+		realrepo="$(resolve_relative_url $repo)" ;;
+	*)
+		# Turn the source into an absolute path if
+		# it is local
+		if base=$(get_repo_base "$repo"); then
+			repo="$base"
+			realrepo=$repo
+		fi
+		;;
+	esac
 
 	# Guess path from repo if not specified or strip trailing slashes
 	if test -z "$path"; then
@@ -122,7 +156,7 @@ module_add()
 	git ls-files --error-unmatch "$path" > /dev/null 2>&1 &&
 	die "'$path' already exists in the index"
 
-	module_clone "$path" "$repo" || exit
+	module_clone "$path" "$realrepo" || exit
 	(unset GIT_DIR && cd "$path" && git checkout -q ${branch:+-b "$branch" "origin/$branch"}) ||
 	die "Unable to checkout submodule '$path'"
 	git add "$path" ||
@@ -153,6 +187,13 @@ modules_init()
 		test -z "$url" &&
 		die "No url found for submodule path '$path' in .gitmodules"
 
+		# Possibly a url relative to parent
+		case "$url" in
+		./*|../*)
+			url="$(resolve_relative_url "$url")"
+			;;
+		esac
+
 		git config submodule."$name".url "$url" ||
 		die "Failed to register url for submodule path '$path'"