[PATCH] setup_work_tree: adjust relative $GIT_WORK_TREE after moving cwd

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

When setup_work_tree() is called, it moves cwd to $GIT_WORK_TREE and
makes internal copy of $GIT_WORK_TREE absolute. The environt variable,
if set by user, remains unchanged. If the variable is relative, it is
no longer correct because its base dir has changed.

Instead of making $GIT_WORK_TREE absolute too, we just say "." and let
subsequent git processes handle it.

Reported-by: Michel Briand <michelbriand@free.fr>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 This one is better, on top of master because the next one is on top
 of nd/setup.

 And I forgot to tell why I did not put the fault in real life [1]
 into tests: I don't like git-merge spawning another process just for
 resetting worktree. Sooner or later it should be replaced to use
 unpack_trees() directly. When that happens, the test would become
 invalid.

 [1] http://thread.gmane.org/gmane.comp.version-control.git/164066/focus=164171

 .gitignore          |    1 +
 Makefile            |    1 +
 setup.c             |    8 ++++++++
 t/t1501-worktree.sh |   11 +++++++++++
 test-subprocess.c   |   21 +++++++++++++++++++++
 5 files changed, 42 insertions(+), 0 deletions(-)
 create mode 100644 test-subprocess.c

diff --git a/.gitignore b/.gitignore
index 87b833c..3dd6ef7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -177,6 +177,7 @@
 /test-sha1
 /test-sigchain
 /test-string-pool
+/test-subprocess
 /test-svn-fe
 /test-treap
 /common-cmds.h
diff --git a/Makefile b/Makefile
index 57d9c65..bdf86a3 100644
--- a/Makefile
+++ b/Makefile
@@ -431,6 +431,7 @@ TEST_PROGRAMS_NEED_X += test-run-command
 TEST_PROGRAMS_NEED_X += test-sha1
 TEST_PROGRAMS_NEED_X += test-sigchain
 TEST_PROGRAMS_NEED_X += test-string-pool
+TEST_PROGRAMS_NEED_X += test-subprocess
 TEST_PROGRAMS_NEED_X += test-svn-fe
 TEST_PROGRAMS_NEED_X += test-treap
 TEST_PROGRAMS_NEED_X += test-index-version
diff --git a/setup.c b/setup.c
index 91887a4..3833569 100644
--- a/setup.c
+++ b/setup.c
@@ -239,6 +239,14 @@ void setup_work_tree(void)
 		git_dir = make_absolute_path(git_dir);
 	if (!work_tree || chdir(work_tree))
 		die("This operation must be run in a work tree");
+
+	/*
+	 * Make sure subsequent git processes find correct worktree
+	 * if $GIT_WORK_TREE is set relative
+	 */
+	if (getenv(GIT_WORK_TREE_ENVIRONMENT))
+		setenv(GIT_WORK_TREE_ENVIRONMENT, ".", 1);
+
 	set_git_dir(make_relative_path(git_dir, work_tree));
 	initialized = 1;
 }
diff --git a/t/t1501-worktree.sh b/t/t1501-worktree.sh
index 2c8f01f..1f3b50d 100755
--- a/t/t1501-worktree.sh
+++ b/t/t1501-worktree.sh
@@ -340,4 +340,15 @@ test_expect_success 'make_relative_path handles double slashes in GIT_DIR' '
 	git --git-dir="$(pwd)//repo.git" --work-tree="$(pwd)" add dummy_file
 '
 
+test_expect_success 'relative $GIT_WORK_TREE and git subprocesses' '
+	(
+	GIT_DIR=repo.git &&
+	GIT_WORK_TREE=repo.git/work &&
+	export GIT_DIR GIT_WORK_TREE &&
+	test-subprocess --setup-work-tree rev-parse --show-toplevel >actual &&
+	echo "`pwd`/repo.git/work" >expected &&
+	test_cmp expected actual
+	)
+'
+
 test_done
diff --git a/test-subprocess.c b/test-subprocess.c
new file mode 100644
index 0000000..667d3e5
--- /dev/null
+++ b/test-subprocess.c
@@ -0,0 +1,21 @@
+#include "cache.h"
+#include "run-command.h"
+
+int main(int argc, char **argv)
+{
+	const char *prefix;
+	struct child_process cp;
+	int nogit = 0;
+
+	prefix = setup_git_directory_gently(&nogit);
+	if (nogit)
+		die("No git repo found");
+	if (!strcmp(argv[1], "--setup-work-tree")) {
+		setup_work_tree();
+		argv++;
+	}
+	memset(&cp, 0, sizeof(cp));
+	cp.git_cmd = 1;
+	cp.argv = (const char **)argv+1;
+	return run_command(&cp);
+}
-- 
1.7.3.4.878.g439c7