t: pass GIT_TRACE through Apache

Apache removes GIT_TRACE from the environment before running
git-http-backend. This can make it hard to debug the server
side of an http session. Let's let it through.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/lib-httpd.sh

@@ -79,6 +79,7 @@ HTTPD_DOCUMENT_ROOT_PATH=$HTTPD_ROOT_PATH/www
 # hack to suppress apache PassEnv warnings
 GIT_VALGRIND=$GIT_VALGRIND; export GIT_VALGRIND
 GIT_VALGRIND_OPTIONS=$GIT_VALGRIND_OPTIONS; export GIT_VALGRIND_OPTIONS
+GIT_TRACE=$GIT_TRACE; export GIT_TRACE
 
 if ! test -x "$LIB_HTTPD_PATH"
 then

t/lib-httpd/apache.conf

@@ -70,6 +70,7 @@ PassEnv GIT_VALGRIND
 PassEnv GIT_VALGRIND_OPTIONS
 PassEnv GNUPGHOME
 PassEnv ASAN_OPTIONS
+PassEnv GIT_TRACE
 
 Alias /dumb/ www/
 Alias /auth/dumb/ www/auth/dumb/