[PATCHv2 1/2] shell setup: clear_local_git_env() function

[Giuseppe Bilotta <giuseppe.bilotta@gmail.com>]

Introduce an auxiliary function to clear all repo-local environment
variables. This should be invoked by any shell script that switches
repository during execution, to ensure that the environment is clean
and that things such as the git dir and worktree are set up correctly.

The list matches the one in git_connect(), so bring them in sync by adding
the missing CONFIG_ENVIRONMENT. Also add a note about the fact that they
should be kept that way.

Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
---
 connect.c       |    2 ++
 git-sh-setup.sh |   15 +++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/connect.c b/connect.c
index 9f39038..12dd0b5 100644
--- a/connect.c
+++ b/connect.c
@@ -583,8 +583,10 @@ struct child_process *git_connect(int fd[2], const char *url_orig,
 	}
 	else {
 		/* remove these from the environment */
+		/* see also clear_local_git_env() in git-sh-setup.sh */
 		const char *env[] = {
 			ALTERNATE_DB_ENVIRONMENT,
+			CONFIG_ENVIRONMENT,
 			DB_ENVIRONMENT,
 			GIT_DIR_ENVIRONMENT,
 			GIT_WORK_TREE_ENVIRONMENT,
diff --git a/git-sh-setup.sh b/git-sh-setup.sh
index 7a09566..f1be832 100644
--- a/git-sh-setup.sh
+++ b/git-sh-setup.sh
@@ -172,6 +172,21 @@ get_author_ident_from_commit () {
 	LANG=C LC_ALL=C sed -ne "$pick_author_script"
 }
 
+# Clear repo-local GIT_* environment variables. Useful when switching to
+# another repository (e.g. when entering a submodule). See also the env
+# list in git_connect()
+clear_local_git_env() {
+	unset	GIT_ALTERNATE_OBJECT_DIRECTORIES \
+		GIT_CONFIG \
+		GIT_DIR \
+		GIT_GRAFT_FILE \
+		GIT_INDEX_FILE \
+		GIT_NO_REPLACE_OBJECTS \
+		GIT_OBJECT_DIRECTORY \
+		GIT_WORKTREE
+
+}
+
 # Make sure we are in a valid repository of a vintage we understand,
 # if we require to be in a git repository.
 if test -z "$NONGIT_OK"
-- 
1.7.0.200.g5ba36.dirty