reset: disallow "reset --keep" outside a work tree

It is safer and consistent with "--merge" and "--hard" resets to disallow
"git reset --keep" outside a work tree.

So let's just do that and add some tests while at it.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-reset.c

@@ -319,7 +319,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	if (reset_type == NONE)
 		reset_type = MIXED; /* by default */
 
-	if (reset_type == HARD || reset_type == MERGE)
+	if (reset_type != SOFT && reset_type != MIXED)
 		setup_work_tree();
 
 	if (reset_type == MIXED && is_bare_repository())

t/t7103-reset-bare.sh

@@ -11,21 +11,26 @@ test_expect_success 'setup non-bare' '
 	git commit -a -m two
 '
 
-test_expect_success 'hard reset requires a worktree' '
+test_expect_success '"hard" reset requires a worktree' '
 	(cd .git &&
 	 test_must_fail git reset --hard)
 '
 
-test_expect_success 'merge reset requires a worktree' '
+test_expect_success '"merge" reset requires a worktree' '
 	(cd .git &&
 	 test_must_fail git reset --merge)
 '
 
-test_expect_success 'mixed reset is ok' '
+test_expect_success '"keep" reset requires a worktree' '
+	(cd .git &&
+	 test_must_fail git reset --keep)
+'
+
+test_expect_success '"mixed" reset is ok' '
 	(cd .git && git reset)
 '
 
-test_expect_success 'soft reset is ok' '
+test_expect_success '"soft" reset is ok' '
 	(cd .git && git reset --soft)
 '
 
@@ -40,19 +45,23 @@ test_expect_success 'setup bare' '
 	cd bare.git
 '
 
-test_expect_success 'hard reset is not allowed in bare' '
+test_expect_success '"hard" reset is not allowed in bare' '
 	test_must_fail git reset --hard HEAD^
 '
 
-test_expect_success 'merge reset is not allowed in bare' '
+test_expect_success '"merge" reset is not allowed in bare' '
 	test_must_fail git reset --merge HEAD^
 '
 
-test_expect_success 'mixed reset is not allowed in bare' '
+test_expect_success '"keep" reset is not allowed in bare' '
+	test_must_fail git reset --keep HEAD^
+'
+
+test_expect_success '"mixed" reset is not allowed in bare' '
 	test_must_fail git reset --mixed HEAD^
 '
 
-test_expect_success 'soft reset is allowed in bare' '
+test_expect_success '"soft" reset is allowed in bare' '
 	git reset --soft HEAD^ &&
 	test "`git show --pretty=format:%s | head -n 1`" = "one"
 '