get_commit_tree(): return NULL for broken tree
authorJeff King <peff@peff.net>
Wed, 10 Apr 2019 02:13:20 +0000 (19:13 -0700)
committerJunio C Hamano <gitster@pobox.com>
Wed, 10 Apr 2019 03:59:39 +0000 (12:59 +0900)
commit834876630b21f832f648bc46a753291e4512ca8f
tree7e01f8442e179e5b3eb130fa408a2b473422eb65
parentb49e74eac480d167c3af8f1286fe520c3d7ce9e1
get_commit_tree(): return NULL for broken tree

Return NULL from 'get_commit_tree()' when a commit's root tree is
corrupt, doesn't exist, or points to an object which is not a tree.

In [1], this situation became a BUG(), but it can certainly occur in
cases which are not a bug in Git, for e.g., if a caller manually crafts
a commit whose tree is corrupt in any of the above ways.

Note that the expect_failure test in t6102 triggers this BUG(), but we
can't flip it to expect_success yet. Solving this problem actually
reveals a second bug.

[1]: 7b8a21dba1 (commit-graph: lazy-load trees for commits, 2018-04-06)

Co-authored-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
commit.c