git-submodule: work with GIT_DIR/GIT_WORK_TREE

The combination of GIT_DIR and GIT_WORK_TREE can be used to manage
files in one directory hierarchy while keeping the repository that
keeps track of them outside the directory hierarchy.  For example:

    git init --bare /path/to/there
    alias dotfiles="GIT_DIR=/path/to/there GIT_WORK_TREE=/path/to/here git"

    cd /path/to/here
    dotfiles add file
    dotfiles commit -a -m "add /path/to/here/file"
    ...

lets you manage files under /path/to/here/ in the repository located
at /path/to/there.

git-submodule however fails to add submodules, as it is confused by
GIT_DIR and GIT_WORK_TREE environment variables when it tries to
work in the submodule, like so:

    dotfiles submodule add http://path.to/submodule
    fatal: working tree '/path/to/here' already exists.

Simply unsetting the environment where the command works on the
submodule is sufficient to fix this, as it has set things up so
that GIT_DIR and GIT_WORK_TREE do not even have to point at the
repository and the working tree of the submodule.

Signed-off-by: Daniel Graña <dangra@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/git-submodule.sh b/git-submodule.sh
index dba4d39..9210f3a 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -181,8 +181,11 @@ module_clone()
 		rm -f "$gitdir/index"
 	else
 		mkdir -p "$gitdir_base"
-		git clone $quiet -n ${reference:+"$reference"} \
-			--separate-git-dir "$gitdir" "$url" "$sm_path" ||
+		(
+			clear_local_git_env
+			git clone $quiet -n ${reference:+"$reference"} \
+				--separate-git-dir "$gitdir" "$url" "$sm_path"
+		) ||
 		die "$(eval_gettext "Clone of '\$url' into submodule path '\$sm_path' failed")"
 	fi