Subject: Re: Minor Bug in git cat-file (git 2.50)?

From: Junio C Hamano <[email-masked]>
Date: Mon, 11 Aug 2025 08:09:28 -0700

Jon Forrest <[email-masked]> writes:

> % ls
> 981922613b2afb6025042ff6bd878ac1994e85
> 981922613b2afb6025042ff6bd878ac1994e86
> % popd
> # use an ambiguous SHA1 prefix
> # why does the next command produce two identical hints, both of which
> # are incorrect?
> % git cat-file -t 78981922613b2afb6025042ff6bd878ac1994e8
> error: short object ID 78981922613b2afb6025042ff6bd878ac1994e8 is
> ambiguous  # this is correct
> hint: The candidates are:
> hint:   7898192 blob
> hint:   7898192 blob
> fatal: Not a valid object name 78981922613b2afb6025042ff6bd878ac1994e8
> # I would have expected:
> hint:   78981922613b2afb6025042ff6bd878ac1994e85 blob
> hint:   78981922613b2afb6025042ff6bd878ac1994e86 blob
> # using the supplied hint doesn't work, which is no surprise
> % git cat-file -t 7898192
> fatal: Not a valid object name 7898192

Fun.

I do not think disambiguation code inspects object validity to
filter out invalid one when computing the shortened object name when
giving hints, so one of these two being a corrupt object should not
have anything to do with this outcome.

Perhaps something like this would help?

 object-name.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git c/object-name.c w/object-name.c
index 11aa0e6afc..13e8a4e47d 100644
--- c/object-name.c
+++ w/object-name.c
@@ -704,7 +704,7 @@ static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
 	while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
 		i++;
 
-	if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
+	if (i < GIT_MAX_HEXSZ && i >= mad->cur_len)
 		mad->cur_len = i + 1;
 
 	return 0;