Inside `git_remote_load`, the calls to `get_optional_config` use
`giterr_clear` to unset any errors that are set due to missing config
keys. If neither a fetch nor a push url config was found for a remote,
we should set an error again.

If we remove a reference while we're iterating through the packed refs,
the position in the iterator will be off.

This lets us work without worrying about what's happening but work on a
snapshot.

These are some issues I found while playing around with the new parser
for docurium.

The documentation has shown this as a single enum for a long time. These
should in fact be two enums. One with the bits for the flags and another
with the bits for the extended flags.

Documentation formatting fixes

…o-remote-found

Remote: Set an error when a remote cannot be found.

Whe already worked out the kinks with the function used in the local
transport. Expose it and make use of it in the local clone method
instead of trying to work it out again.

Concurrent ref iterator access

clone: re-use the local transport's path resolution