git show HEAD:$ambiguous
'
+test_expect_success 'rewrite repository including refs that point at non-commit object' '
+ test_when_finished "git reset --hard original" &&
+ tree=$(git rev-parse HEAD^{tree}) &&
+ test_when_finished "git replace -d $tree" &&
+ echo A >new &&
+ git add new &&
+ new_tree=$(git write-tree) &&
+ git replace $tree $new_tree &&
+ git tag -a -m "tag to a tree" treetag $new_tree &&
+ git reset --hard HEAD &&
+ git filter-branch -f -- --all >filter-output 2>&1 &&
+ ! fgrep fatal filter-output
+'
+
test_done