rev-parse: respect core.hooksPath in --git-path

The idea of the --git-path option is not only to avoid having to
prefix paths with the output of --git-dir all the time, but also to
respect overrides for specific common paths inside the .git directory
(e.g. `git rev-parse --git-path objects` will report the value of the
environment variable GIT_OBJECT_DIRECTORY, if set).

When introducing the core.hooksPath setting, we forgot to adjust
git_path() accordingly. This patch fixes that.

While at it, revert the special-casing of core.hooksPath in
run-command.c, as it is now no longer needed.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/t1350-config-hooks-path.sh b/t/t1350-config-hooks-path.sh
index 5e3fb3a..f1f9aee 100755
--- a/t/t1350-config-hooks-path.sh
+++ b/t/t1350-config-hooks-path.sh
@@ -34,4 +34,10 @@
 	test_cmp expect actual
 '
 
+test_expect_success 'git rev-parse --git-path hooks' '
+	git config core.hooksPath .git/custom-hooks &&
+	git rev-parse --git-path hooks/abc >actual &&
+	test .git/custom-hooks/abc = "$(cat actual)"
+'
+
 test_done