t5510-fetch: run non-httpd-specific test before sourcing 'lib-httpd.sh'

't5510-fetch.sh' sources 'lib-httpd.sh' near the end to run a
httpd-specific test, but 'lib-httpd.sh' skips all the rest of the test
script if the dependencies for running httpd tests are not fulfilled.
Alas, recently cdbd70c437 (fetch: add --[no-]show-forced-updates
argument, 2019-06-18) appended a non-httpd-specific test at the end,
and this test is then skipped as well when httpd tests can't be run.

Move this new test earlier in the test script, before 'lib-httpd.sh'
is sourced, so it will be run even when httpd tests aren't.

Also add a comment at the end of this test script to warn against
adding non-httpd-specific tests at the end, in the hope that it will
help prevent similar issues in the future.

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

t/t5510-fetch.sh

@@ -902,6 +902,29 @@ test_expect_success C_LOCALE_OUTPUT 'fetch compact output' '
 	test_cmp expect actual
 '
 
+test_expect_success '--no-show-forced-updates' '
+	mkdir forced-updates &&
+	(
+		cd forced-updates &&
+		git init &&
+		test_commit 1 &&
+		test_commit 2
+	) &&
+	git clone forced-updates forced-update-clone &&
+	git clone forced-updates no-forced-update-clone &&
+	git -C forced-updates reset --hard HEAD~1 &&
+	(
+		cd forced-update-clone &&
+		git fetch --show-forced-updates origin 2>output &&
+		test_i18ngrep "(forced update)" output
+	) &&
+	(
+		cd no-forced-update-clone &&
+		git fetch --no-show-forced-updates origin 2>output &&
+		test_i18ngrep ! "(forced update)" output
+	)
+'
+
 setup_negotiation_tip () {
 	SERVER="$1"
 	URL="$2"
@@ -978,27 +1001,7 @@ test_expect_success '--negotiation-tip limits "have" lines sent with HTTP protoc
 	check_negotiation_tip
 '
 
-test_expect_success '--no-show-forced-updates' '
-	mkdir forced-updates &&
-	(
-		cd forced-updates &&
-		git init &&
-		test_commit 1 &&
-		test_commit 2
-	) &&
-	git clone forced-updates forced-update-clone &&
-	git clone forced-updates no-forced-update-clone &&
-	git -C forced-updates reset --hard HEAD~1 &&
-	(
-		cd forced-update-clone &&
-		git fetch --show-forced-updates origin 2>output &&
-		test_i18ngrep "(forced update)" output
-	) &&
-	(
-		cd no-forced-update-clone &&
-		git fetch --no-show-forced-updates origin 2>output &&
-		test_i18ngrep ! "(forced update)" output
-	)
-'
+# DO NOT add non-httpd-specific tests here, because the last part of this
+# test script is only executed when httpd is available and enabled.
 
 test_done