This changes the behavior of object parsing for commits and tags
so that even when bad data is found inside the object, we will
continue to try to parse as much of the object as we can.  The
existing functions (`git_object_lookup` for example) will still
delete the partially parsed object before returning an error, but
this also adds a new function `git_object_lookup_lax` that will
still return the error, but will also return the object with the
partial data (if we got far enough along in the parsing process to
even create the base object).

Initialize local variable

And decrease extra reload checks of config data.

Improve checks for ignore containment

Make pack object lookup use loops

The code doesn't use SSL and a test requires it.

The base object is a good cache candidate, so we shouldn't forget to add
it to the cache.