Merge branch 'jk/warn-on-object-refname-ambiguity'

* jk/warn-on-object-refname-ambiguity:
rev-list: disable object/refname ambiguity check with --stdin
cat-file: restore warn_on_object_refname_ambiguity flag
cat-file: fix a minor memory leak in batch_objects
cat-file: refactor error handling of batch_objects

diff --cc builtin/cat-file.c
Simple merge

diff --cc revision.c
Simple merge