gc + p4 tests: use "test_hook", remove sub-shells

Refactor the repository setup code for tests that test hooks the use
of sub-shells when setting up the test repository and hooks, and use
the "test_hook" wrapper instead of "write_scripts".

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6500-gc.sh

@@ -101,12 +101,12 @@ test_expect_success 'pre-auto-gc hook can stop auto gc' '
 	EOF
 
 	git init pre-auto-gc-hook &&
+	test_hook -C pre-auto-gc-hook pre-auto-gc <<-\EOF &&
+	echo >&2 no gc for you &&
+	exit 1
+	EOF
 	(
 		cd pre-auto-gc-hook &&
-		write_script ".git/hooks/pre-auto-gc" <<-\EOF &&
-		echo >&2 no gc for you &&
-		exit 1
-		EOF
 
 		git config gc.auto 3 &&
 		git config gc.autoDetach false &&
@@ -128,14 +128,12 @@ test_expect_success 'pre-auto-gc hook can stop auto gc' '
 	See "git help gc" for manual housekeeping.
 	EOF
 
-	(
-		cd pre-auto-gc-hook &&
-		write_script ".git/hooks/pre-auto-gc" <<-\EOF &&
-		echo >&2 will gc for you &&
-		exit 0
-		EOF
-		git gc --auto >../out.actual 2>../err.actual
-	) &&
+	test_hook -C pre-auto-gc-hook --clobber pre-auto-gc <<-\EOF &&
+	echo >&2 will gc for you &&
+	exit 0
+	EOF
+
+	git -C pre-auto-gc-hook gc --auto >out.actual 2>err.actual &&
 
 	test_must_be_empty out.actual &&
 	test_cmp err.expect err.actual

t/t9800-git-p4-basic.sh

@@ -277,16 +277,21 @@ test_expect_success 'run hook p4-pre-submit before submit' '
 		git commit -m "add hello.txt" &&
 		git config git-p4.skipSubmitEdit true &&
 		git p4 submit --dry-run >out &&
-		grep "Would apply" out &&
-		mkdir -p .git/hooks &&
-		write_script .git/hooks/p4-pre-submit <<-\EOF &&
-		exit 0
-		EOF
+		grep "Would apply" out
+	) &&
+	test_hook -C "$git" p4-pre-submit <<-\EOF &&
+	exit 0
+	EOF
+	(
+		cd "$git" &&
 		git p4 submit --dry-run >out &&
-		grep "Would apply" out &&
-		write_script .git/hooks/p4-pre-submit <<-\EOF &&
-		exit 1
-		EOF
+		grep "Would apply" out
+	) &&
+	test_hook -C "$git" --clobber p4-pre-submit <<-\EOF &&
+	exit 1
+	EOF
+	(
+		cd "$git" &&
 		test_must_fail git p4 submit --dry-run >errs 2>&1 &&
 		! grep "Would apply" errs
 	)