t/lib-httpd: add the strip_access_log() helper function

Four tests in three httpd-related test scripts check the contents of
Apache's 'access.log', and they all do so by running 'sed' with the
exact same script consisting of four s/// commands to strip
uninteresting log fields and to vertically align the requested URLs.

Extract this into a common helper function 'strip_access_log' in
'lib-httpd.sh', and use it in all of those tests.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-httpd.sh

@@ -287,3 +287,12 @@ expect_askpass() {
 	test_cmp "$TRASH_DIRECTORY/askpass-expect" \
 		 "$TRASH_DIRECTORY/askpass-query"
 }
+
+strip_access_log() {
+	sed -e "
+		s/^.* \"//
+		s/\"//
+		s/ [1-9][0-9]*\$//
+		s/^GET /GET  /
+	" "$HTTPD_ROOT_PATH"/access.log
+}