Re: [PATCH v2] run-command: add hint when a hook is ignored

Damien Marié [off-list ref] writes:

 	if (access(path.buf, X_OK) < 0) {
+		int err = errno;

OK, so we remember how/why we failed in err.

 #ifdef STRIP_EXTENSION
 		strbuf_addstr(&path, STRIP_EXTENSION);
 		if (access(path.buf, X_OK) >= 0)
 			return path.buf;
+		else if (errno == EACCES)
+			err = errno;

I think it is easier to reason about if this were not "else if", but
just a simple "if".

 - We tried foo-hook, and failed.
 - On a platform that foo-hook.exe can also be a hook
   - We try foo-hook.exe and if it seems OK, we return with smile.
   - If not, if we know foo-hook.exe exists but we cannot execute,
     we update err (forgetting the reason why foo-hook was wrong)
     with the reason why foo-hook.exe is bad.

It is OK to forget why foo-hook was unhappy, as on a STRIP_EXTENSION
build, we would have tried to run foo-hook.exe anyway.

 #endif

So at this point, with or without STRIP_EXTENSION, err tells us why
the file we wanted to be available as a hook did not pass our
criteria.

+		if (err == EACCES && advice_ignored_hook) {

And we want to do the advise thing only if we know we failed due to
EACCES and for no other reason.

+			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;

Overall, the logic looks correct to me.  Note that we may have
gotten EACCES not because the path lacked the executable bit, but
because the hook directory was unreadable ;-), but in such a case,
you cannot tell if "it's not set as executable" is true anyway.

These days, things like this...

+# install hook that always succeeds
+HOOKDIR="$(git rev-parse --git-dir)/hooks"
+HOOK="$HOOKDIR/pre-commit"
+mkdir -p "$HOOKDIR"
+cat > "$HOOK" <<EOF
+#!/bin/sh
+exit 0
+EOF
+
+chmod +x "$HOOK"

...should all go to test_expect_success, i.e.

	test_expect_success setup '
		...
		mkdir -p "$hookdir" &&
		write_script "$hookdir/pre-commit" <<-\EOF
		exit 0
		EOF
	'

write_script takes care of flipping +x on.

+test_expect_success 'no warning if proper hook' '
+
+    if git commit -m "more" 2>&1 >/dev/null | grep hint
+    then
+        false
+    else
+        true
+    fi
+

 - Indents in our shell scripts are done with tab (HT).

 - We try to avoid running git command on the LHS of a pipe when we
   do not have to.

 - "git commit" may fail due to not having anything worth
   committing, even before it notices that pre-commit hook is or is
   not executable.  Avoid relying on the order of things that happen
   to be true in the current implementation when we do not have to.

 - We may see some other hint.  Avoid relying on the set of advises
   that happens to currently be defined when we do not have to.

 - Output from advise() can be localized, so grepping to expect
   something either is there or is not there would be triggered as
   an error in GETTEXT_POISON build.  We unfortunately need to use
   test_i18ngrep to work it around.

Perhaps the above should become more like so:

	git commit --allow-empty -m more 2>message &&
	test_i18ngrep ! "hook was ignored" message

+'
+
+chmod -x "$HOOK"

Move this to the beginning of the next one that is protected with
POSIXPERM.

+test_expect_success POSIXPERM 'warning if hook not set as executable' '
+
+    if git commit -m "more" 2>&1 >/dev/null | grep hint
+    then
+        true
+    else
+        false
+    fi
+'

	chmod -x "$hookdir/pre-commit" &&
	git commit --allow-empty -m "even more" 2>message &&
	test_i18ngrep "hook was ignored" message

or something like that.

Thanks.