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>

git-submodule.sh

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

t/t7409-submodule-detached-worktree.sh

@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# Copyright (c) 2012 Daniel Graña
+#
+
+test_description='Test submodules on detached working tree
+
+This test verifies that "git submodule" initialization, update and addition works
+on detahced working trees
+'
+
+TEST_NO_CREATE_REPO=1
+. ./test-lib.sh
+
+test_expect_success 'submodule on detached working tree' '
+	git init --bare remote &&
+	test_create_repo bundle1 &&
+	(cd bundle1 && test_commit "shoot") &&
+	mkdir home &&
+	(
+		cd home &&
+		export GIT_WORK_TREE="$(pwd)" GIT_DIR="$(pwd)/.dotfiles" &&
+		git clone --bare ../remote .dotfiles &&
+		git submodule add ../bundle1 .vim/bundle/sogood &&
+		test_commit "sogood" &&
+		git push origin master
+	) &&
+	mkdir home2 &&
+	(
+		cd home2 &&
+		export GIT_WORK_TREE="$(pwd)" GIT_DIR="$(pwd)/.dotfiles" &&
+		git clone --bare ../remote .dotfiles &&
+		git submodule update --init
+	)
+'
+
+test_expect_success 'submodule on detached working pointed by core.worktree' '
+	mkdir home3 &&
+	(
+		cd home3 &&
+		export GIT_DIR="$(pwd)/.dotfiles" &&
+		git clone --bare ../remote "$GIT_DIR" &&
+		git config core.bare false &&
+		git config core.worktree .. &&
+		git submodule add ../bundle1 .vim/bundle/dupe &&
+		test_commit "dupe" &&
+		git push origin master
+	) &&
+	(
+		cd home &&
+		export GIT_DIR="$(pwd)/.dotfiles" &&
+		git config core.bare false &&
+		git config core.worktree .. &&
+		git pull &&
+		git submodule update &&
+		git submodule status &&
+		test -d .vim/bundle/dupe
+	)
+'
+
+test_done