t5550-http-fetch: Use subshell for repository operations

Change into the server repository's directory using a subshell,
so we can return back to the top of the trash directory before
doing anything more in the test script.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5550-http-fetch.sh

@@ -55,9 +55,10 @@ test_expect_success 'http remote detects correct HEAD' '
 
 test_expect_success 'fetch packed objects' '
 	cp -R "$HTTPD_DOCUMENT_ROOT_PATH"/repo.git "$HTTPD_DOCUMENT_ROOT_PATH"/repo_pack.git &&
-	cd "$HTTPD_DOCUMENT_ROOT_PATH"/repo_pack.git &&
-	git --bare repack &&
-	git --bare prune-packed &&
+	(cd "$HTTPD_DOCUMENT_ROOT_PATH"/repo_pack.git &&
+	 git --bare repack &&
+	 git --bare prune-packed
+	) &&
 	git clone $HTTPD_URL/dumb/repo_pack.git
 '