hook: accept .enabled and .parallel given without a value

hook.<name>.enabled and hook.<name>.parallel are booleans, and
git-config(1) documents a boolean without a value as true. But
hook_config_lookup_all() rejects every hook.<name>.<key> that has no
value, so "git -c hook.lint.parallel hook run pre-commit" fails with
"missing value for 'hook.lint.parallel'", and so does a bare
"parallel" under [hook "lint"]. The same happens with .enabled, for a
hook as well as for an event.

Keep rejecting a missing value for the other keys. For .enabled and
.parallel, pass it to git_parse_maybe_bool(), which takes it as true.

Assisted-by: Claude Fable 5.1
Signed-off-by: Thomas Bachem <mail@thomasbachem.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

hook.c

@@ -184,7 +184,8 @@ static int hook_config_lookup_all(const char *key, const char *value,
 		return 0;
 	}
 
-	if (!value)
+	/* .enabled and .parallel are bools, where a missing value means true */
+	if (!value && strcmp(subkey, "enabled") && strcmp(subkey, "parallel"))
 		return config_error_nonbool(key);
 
 	/* Extract name, ensuring it is null-terminated. */

t/t1800-hook.sh

@@ -516,6 +516,17 @@ test_expect_success 'globally disabled hook can be re-enabled locally' '
 	test_cmp expected actual
 '
 
+test_expect_success 'hook.<friendly-name>.enabled without a value means true' '
+	test_config_global hook.global-hook.event "test-hook" &&
+	test_config_global hook.global-hook.command "echo \"global-hook ran\"" &&
+	test_config_global hook.global-hook.enabled false &&
+
+	echo "global-hook ran" >expected &&
+	git -c hook.global-hook.enabled \
+		hook run --allow-unknown-hook-name test-hook 2>actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'configured hooks run before hookdir hook' '
 	setup_hookdir &&
 	test_config hook.first.event "pre-commit" &&
@@ -1080,6 +1091,17 @@ test_expect_success 'hook.jobs=-1 resolves to online_cpus()' '
 	test_grep "\"region_enter\".*\"hook\".*\"test-hook\".*\"max:$cpus\"" trace.txt
 '
 
+test_expect_success 'hook.<friendly-name>.parallel without a value means true' '
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command "true" &&
+	test_config hook.jobs 2 &&
+
+	GIT_TRACE2_EVENT="$(pwd)/trace-parallel.txt" \
+		git -c hook.hook-1.parallel \
+		hook run --allow-unknown-hook-name test-hook >out 2>err &&
+	test_grep "\"region_enter\".*\"hook\".*\"test-hook\".*\"max:2\"" trace-parallel.txt
+'
+
 test_expect_success 'hook.<event>.jobs=-1 resolves to online_cpus()' '
 	test_config hook.hook-1.event test-hook &&
 	test_config hook.hook-1.command "true" &&