+# Clone a submodule
+#
+# Prior to calling, modules_update checks that a possibly existing
+# path is not a git repository.
+# Likewise, module_add checks that path does not exist at all,
+# since it is the location of a new submodule.
+#
+module_clone()
+{
+ path=$1
+ url=$2
+
+ # If there already is a directory at the submodule path,
+ # expect it to be empty (since that is the default checkout
+ # action) and try to remove it.
+ # Note: if $path is a symlink to a directory the test will
+ # succeed but the rmdir will fail. We might want to fix this.
+ if test -d "$path"
+ then
+ rmdir "$path" 2>/dev/null ||
+ die "Directory '$path' exist, but is neither empty nor a git repository"
+ fi
+
+ test -e "$path" &&
+ die "A file already exist at path '$path'"
+
+ git-clone -n "$url" "$path" ||
+ die "Clone of '$url' into submodule path '$path' failed"
+}
+
+#
+# Add a new submodule to the working tree, .gitmodules and the index
+#
+# $@ = repo [path]
+#
+# optional branch is stored in global branch variable
+#
+module_add()
+{
+ repo=$1
+ path=$2
+
+ if test -z "$repo"; then
+ usage
+ fi
+
+ # Turn the source into an absolute path if
+ # it is local
+ if base=$(get_repo_base "$repo"); then
+ repo="$base"
+ fi
+
+ # Guess path from repo if not specified or strip trailing slashes
+ if test -z "$path"; then
+ path=$(echo "$repo" | sed -e 's|/*$||' -e 's|:*/*\.git$||' -e 's|.*[/:]||g')
+ else
+ path=$(echo "$path" | sed -e 's|/*$||')
+ fi
+
+ test -e "$path" &&
+ die "'$path' already exists"
+
+ git ls-files --error-unmatch "$path" > /dev/null 2>&1 &&
+ die "'$path' already exists in the index"
+
+ module_clone "$path" "$repo" || exit
+ (unset GIT_DIR && cd "$path" && git checkout -q ${branch:+-b "$branch" "origin/$branch"}) ||
+ die "Unable to checkout submodule '$path'"
+ git add "$path" ||
+ die "Failed to add submodule '$path'"
+
+ GIT_CONFIG=.gitmodules git config submodule."$path".path "$path" &&
+ GIT_CONFIG=.gitmodules git config submodule."$path".url "$repo" &&
+ git add .gitmodules ||
+ die "Failed to register submodule '$path'"
+}
+
+#
+# Register submodules in .git/config