run-command: add hint when a hook is ignored

When an hook is present but the file is not set as executable then git will
ignore the hook.
For now this is silent which can be confusing.

This commit adds this warning to improve the situation:

  hint: The 'pre-commit' hook was ignored because it's not set as executable.
  hint: You can disable this warning with `git config advice.ignoredHook false`

To allow the old use-case of enabling/disabling hooks via the executable flag a
new setting is introduced: advice.ignoredHook.

Signed-off-by: Damien Marié <damien@dam.io>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -351,6 +351,9 @@ advice.*::
 	addEmbeddedRepo::
 		Advice on what to do when you've accidentally added one
 		git repo inside of another.
+	ignoredHook::
+		Advice shown if an hook is ignored because the hook is not
+		set as executable.
 --
 
 core.fileMode::

advice.c

@@ -17,6 +17,7 @@ int advice_set_upstream_failure = 1;
 int advice_object_name_warning = 1;
 int advice_rm_hints = 1;
 int advice_add_embedded_repo = 1;
+int advice_ignored_hook = 1;
 
 static struct {
 	const char *name;
@@ -38,6 +39,7 @@ static struct {
 	{ "objectnamewarning", &advice_object_name_warning },
 	{ "rmhints", &advice_rm_hints },
 	{ "addembeddedrepo", &advice_add_embedded_repo },
+	{ "ignoredhook", &advice_ignored_hook },
 
 	/* make this an alias for backward compatibility */
 	{ "pushnonfastforward", &advice_push_update_rejected }

advice.h

@@ -19,6 +19,7 @@ extern int advice_set_upstream_failure;
 extern int advice_object_name_warning;
 extern int advice_rm_hints;
 extern int advice_add_embedded_repo;
+extern int advice_ignored_hook;
 
 int git_default_advice_config(const char *var, const char *value);
 __attribute__((format (printf, 1, 2)))

contrib/completion/git-completion.bash

@@ -2350,6 +2350,7 @@ _git_config ()
 		advice.rmHints
 		advice.statusHints
 		advice.statusUoption
+		advice.ignoredHook
 		alias.
 		am.keepcr
 		am.threeWay

run-command.c

@@ -5,6 +5,7 @@
 #include "argv-array.h"
 #include "thread-utils.h"
 #include "strbuf.h"
+#include "string-list.h"
 
 void child_process_init(struct child_process *child)
 {
@@ -1169,11 +1170,28 @@ const char *find_hook(const char *name)
 	strbuf_reset(&path);
 	strbuf_git_path(&path, "hooks/%s", name);
 	if (access(path.buf, X_OK) < 0) {
+		int err = errno;
+
 #ifdef STRIP_EXTENSION
 		strbuf_addstr(&path, STRIP_EXTENSION);
 		if (access(path.buf, X_OK) >= 0)
 			return path.buf;
+		if (errno == EACCES)
+			err = errno;
 #endif
+
+		if (err == EACCES && advice_ignored_hook) {
+			static struct string_list advise_given = STRING_LIST_INIT_DUP;
+
+			if (!string_list_lookup(&advise_given, name)) {
+				string_list_insert(&advise_given, name);
+				advise(_("The '%s' hook was ignored because "
+					 "it's not set as executable.\n"
+					 "You can disable this warning with "
+					 "`git config advice.ignoredHook false`."),
+				       path.buf);
+			}
+		}
 		return NULL;
 	}
 	return path.buf;

t/t7520-ignored-hook-warning.sh

@@ -0,0 +1,41 @@
+#!/bin/sh
+
+test_description='ignored hook warning'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	hookdir="$(git rev-parse --git-dir)/hooks" &&
+	hook="$hookdir/pre-commit" &&
+	mkdir -p "$hookdir" &&
+	write_script "$hook" <<-\EOF
+	exit 0
+	EOF
+'
+
+test_expect_success 'no warning if hook is not ignored' '
+	git commit --allow-empty -m "more" 2>message &&
+	test_i18ngrep ! -e "hook was ignored" message
+'
+
+test_expect_success POSIXPERM 'warning if hook is ignored' '
+	chmod -x "$hook" &&
+	git commit --allow-empty -m "even more" 2>message &&
+	test_i18ngrep -e "hook was ignored" message
+'
+
+test_expect_success POSIXPERM 'no warning if advice.ignoredHook set to false' '
+	test_config advice.ignoredHook false &&
+	chmod -x "$hook" &&
+	git commit --allow-empty -m "even more" 2>message &&
+	test_i18ngrep ! -e "hook was ignored" message
+'
+
+test_expect_success 'no warning if unset advice.ignoredHook and hook removed' '
+	rm -f "$hook" &&
+	test_unconfig advice.ignoredHook &&
+	git commit --allow-empty -m "even more" 2>message &&
+	test_i18ngrep ! -e "hook was ignored" message
+'
+
+test_done