setup: Provide GIT_PREFIX to built-ins

GIT_PREFIX was added in 7cf16a14f5c070f7b14cf28023769450133172ae so that
aliases can know the directory from which a !alias was called.

Knowing the prefix relative to the root is helpful in other programs
so export it to built-ins as well.

Helped-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/setup.c b/setup.c
index 03cd84f2fc..63f5368d90 100644
--- a/setup.c
+++ b/setup.c
@@ -602,6 +602,11 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	const char *prefix;
 
 	prefix = setup_git_directory_gently_1(nongit_ok);
+	if (prefix)
+		setenv("GIT_PREFIX", prefix, 1);
+	else
+		setenv("GIT_PREFIX", "", 1);
+
 	if (startup_info) {
 		startup_info->have_repository = !nongit_ok || !*nongit_ok;
 		startup_info->prefix = prefix;