fsck: support ignoring objects in `git fsck` via fsck.skiplist
Identical to support in `git receive-pack for the config option
`receive.fsck.skiplist`, we now support ignoring given objects in
`git fsck` via `fsck.skiplist` altogether.
This is extremely handy in case of legacy repositories where it would
cause more pain to change incorrect objects than to live with them
(e.g. a duplicate 'author' line in an early commit object).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>