* remote: always populate old id in update tips by @ethomson in https://github.com/libgit2/libgit2/pull/6506
The update tips callback would not always be properly provided with an empty (`0000000...`) OID for new refs.
* Revert #6503 by @ethomson in https://github.com/libgit2/libgit2/pull/6511
The certificate callback added port information for callbacks in #6503, but the format was ambiguous with IPv6 addresses. Revert this change temporarily.
* Add `git_odb_backend_loose` back by @ethomson in https://github.com/libgit2/libgit2/pull/6512
During SHA256 refactoring, the `git_odb_backend_loose` API was accidentally removed. Add it back.
* meta: configure pkg-config .pc correctly by @ethomson in https://github.com/libgit2/libgit2/pull/6514
During SHA256 refactoring, the pkg-config `.pc` file was erroneously renamed to `git2` instead of `libgit2`. Repair this.
