On Wed, Aug 24, 2022 at 10:20:30PM -0700, Junio C Hamano wrote:

* sy/mv-out-of-cone (2022-08-10) 9 commits
  (merged to 'next' on 2022-08-17 at 2316d9ce4d)
 + mv: check overwrite for in-to-out move
 + advice.h: add advise_on_moving_dirty_path()
 + mv: cleanup empty WORKING_DIRECTORY
 + mv: from in-cone to out-of-cone
 + mv: remove BOTH from enum update_mode
 + mv: check if <destination> is a SKIP_WORKTREE_DIR
 + mv: free the with_slash in check_dir_in_index()
 + mv: rename check_dir_in_index() to empty_dir_has_sparse_contents()
 + t7002: add tests for moving from in-cone to out-of-cone

 "git mv A B" in a sparsely populated working tree can be asked to
 move a path from a directory that is "in cone" to another directory
 that is "out of cone".  Handling of such a case has been improved.

 Will merge to 'master'.
 source: [ref]

This topic (and now 'next') segfaults with SANITIZE=address in t7001.
The problem is running:

  git mv path1/path2/ .

The "." in the destination is normalized to the empty string by
internal_prefix_pathspec(). But commit c08830de41 (mv: check if
<destination> is a SKIP_WORKTREE_DIR, 2022-08-09) then calls add_slash()
on the result, and it isn't prepared to see an empty string.

This makes the problem go away:

diff --git a/builtin/mv.c b/builtin/mv.c
index 11aea7b4db..6c6385dbb5 100644
--- a/builtin/mv.c
+++ b/builtin/mv.c

@@ -72,7 +72,7 @@ static const char **internal_prefix_pathspec(const char *prefix,
 static const char *add_slash(const char *path)
 {
 	size_t len = strlen(path);
-	if (path[len - 1] != '/') {
+	if (len && path[len - 1] != '/') {
 		char *with_slash = xmalloc(st_add(len, 2));
 		memcpy(with_slash, path, len);
 		with_slash[len++] = '/';

but I didn't follow the topic well enough to know if there's anything
subtle (i.e., I'm not sure why we need the slash in the first place, and
whether "./" would be more appropriate, etc). So punting to folks who
were involved. :)

-Peff