tree-walk: be more specific about corrupt tree errors
When the tree-walker runs into an error, it just calls
die(), and the message is always "corrupt tree file".
However, we are actually covering several cases here; let's
give the user a hint about what happened.
Let's also avoid using the word "corrupt", which makes it
seem like the data bit-rotted on disk. Our sha1 check would
already have found that. These errors are ones of data that
is malformed in the first place.
Signed-off-by: David Turner <dturner@twosigma.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>