Re* [PATCH 2/2] check-ignore.c: fix segfault with '.' argument from repo root

[Junio C Hamano <gitster@pobox.com>]

Adam Spiers <git@adamspiers.org> writes:

> Fair enough.  I'll reply to this with a new version.[0]
>
> [0] I wish there was a clean way to include the new version inline,
>     but as I've noted before, there doesn't seem to be:
>
>     http://article.gmane.org/gmane.comp.version-control.git/146110

I find it easier to later find the patch if you made it a separate
follow-up like you did, but you can do it this way if you really
want to, using a scissors line, like so.  Please do not try to be
creative and change the shape of scissors just for the sake of
chaning it.

-- >8 --
Subject: name-hash: allow hashing an empty string

Usually we do not pass an empty string to the function hash_name()
because we almost always ask for hash values for a path that is a
candidate to be added to the index. However, check-ignore (and most
likely check-attr, but I didn't check) apparently has a callchain
to ask the hash value for an empty path when it was given a "." from
the top-level directory to ask "Is the path . excluded by default?"

Make sure that hash_name() does not overrun the end of the given
pathname even when it is empty.

Also remove a sweep-the-issue-under-the-rug conditional in
check-ignore that avoided to pass an empty string to the callchain.

Signed-off-by: Adam Spiers <git@adamspiers.org>
---
 builtin/check-ignore.c | 2 +-
 name-hash.c            | 4 ++--
 t/t0008-ignores.sh     | 5 +++++
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/builtin/check-ignore.c b/builtin/check-ignore.c
index 709535c..0240f99 100644
--- a/builtin/check-ignore.c
+++ b/builtin/check-ignore.c
@@ -89,7 +89,7 @@ static int check_ignore(const char *prefix, const char **pathspec)
 					? strlen(prefix) : 0, path);
 		full_path = check_path_for_gitlink(full_path);
 		die_if_path_beyond_symlink(full_path, prefix);
-		if (!seen[i] && path[0]) {
+		if (!seen[i]) {
 			exclude = last_exclude_matching_path(&check, full_path,
 							     -1, &dtype);
 			if (exclude) {
diff --git a/name-hash.c b/name-hash.c
index d8d25c2..942c459 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -24,11 +24,11 @@ static unsigned int hash_name(const char *name, int namelen)
 {
 	unsigned int hash = 0x123;
 
-	do {
+	while (namelen--) {
 		unsigned char c = *name++;
 		c = icase_hash(c);
 		hash = hash*101 + c;
-	} while (--namelen);
+	}
 	return hash;
 }
 
diff --git a/t/t0008-ignores.sh b/t/t0008-ignores.sh
index ebe7c70..9c1bde1 100755
--- a/t/t0008-ignores.sh
+++ b/t/t0008-ignores.sh
@@ -138,6 +138,7 @@ test_expect_success 'setup' '
 	cat <<-\EOF >.gitignore &&
 		one
 		ignored-*
+		top-level-dir/
 	EOF
 	for dir in . a
 	do
@@ -177,6 +178,10 @@ test_expect_success 'setup' '
 #
 # test invalid inputs
 
+test_expect_success_multi '. corner-case' '' '
+	test_check_ignore . 1
+'
+
 test_expect_success_multi 'empty command line' '' '
 	test_check_ignore "" 128 &&
 	stderr_contains "fatal: no path specified"