[PATCH 4/6] check_filename(): handle ":^" path magic

[Jeff King <peff@peff.net>]

We special-case "git log :/foo" to work when "foo" exists in
the working tree. But :^ (and its alias :!) do not get the
same treatment, requiring the user to supply a
disambiguating "--". Let's make them work without requiring
the user to type the "--".

Signed-off-by: Jeff King <peff@peff.net>
---
 setup.c                       |  4 ++++
 t/t4208-log-magic-pathspec.sh | 13 +++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/setup.c b/setup.c
index f2a8070bd..86bb7c9a9 100644
--- a/setup.c
+++ b/setup.c
@@ -141,6 +141,10 @@ int check_filename(const char *prefix, const char *arg)
 		if (!*arg) /* ":/" is root dir, always exists */
 			return 1;
 		prefix = NULL;
+	} else if (skip_prefix(arg, ":!", &arg) ||
+		   skip_prefix(arg, ":^", &arg)) {
+		if (!*arg) /* excluding everything is silly, but allowed */
+			return 1;
 	}
 
 	if (prefix)
diff --git a/t/t4208-log-magic-pathspec.sh b/t/t4208-log-magic-pathspec.sh
index 70bc64100..67250ebdc 100755
--- a/t/t4208-log-magic-pathspec.sh
+++ b/t/t4208-log-magic-pathspec.sh
@@ -52,6 +52,19 @@ test_expect_success 'git log HEAD -- :/' '
 	test_cmp expected actual
 '
 
+test_expect_success '"git log :^sub" is not ambiguous' '
+	git log :^sub
+'
+
+test_expect_success '"git log :^does-not-exist" does not match anything' '
+	test_must_fail git log :^does-not-exist
+'
+
+test_expect_success  '"git log :!" behaves the same as :^' '
+	git log :!sub &&
+	test_must_fail git log :!does-not-exist
+'
+
 test_expect_success 'command line pathspec parsing for "git log"' '
 	git reset --hard &&
 	>a &&
-- 
2.13.0.496.ge44ba89db