environment: add GIT_PREFIX to local_repo_env

The GIT_PREFIX variable is set based on our location within
the working tree. It should therefore be cleared whenever
GIT_WORK_TREE is cleared.

In practice, this doesn't cause any bugs, because none of
the sub-programs we invoke with local_repo_env cleared
actually care about GIT_PREFIX. But this is the right thing
to do, and future proofs us against that assumption changing.

While we're at it, let's define a GIT_PREFIX_ENVIRONMENT
macro; this avoids repetition of the string literal, which
can help catch any spelling mistakes in the code.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/setup.c b/setup.c
index 1b120175f2..d0e3ecdcd4 100644
--- a/setup.c
+++ b/setup.c
@@ -768,9 +768,9 @@ const char *setup_git_directory_gently(int *nongit_ok)
 
 	prefix = setup_git_directory_gently_1(nongit_ok);
 	if (prefix)
-		setenv("GIT_PREFIX", prefix, 1);
+		setenv(GIT_PREFIX_ENVIRONMENT, prefix, 1);
 	else
-		setenv("GIT_PREFIX", "", 1);
+		setenv(GIT_PREFIX_ENVIRONMENT, "", 1);
 
 	if (startup_info) {
 		startup_info->have_repository = !nongit_ok || !*nongit_ok;