Ghrepo

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- Drop support for Python 3.6
- Support Python 3.11
- Properly follow RFC 3986 when parsing username & password fields in
`www.github.com` URLs
- Correct the accepted format for URLs that start with `ssh://` (They need to
separate the hostname from the path with a slash rather than a colon)
- Schemes & hostnames in URLs are now parsed case-insensitively
- CLI: Don't show superfluous error traceback when the given repo does not
possess the given remote

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- `get_local_repo()` now raises a dedicated `NoSuchRemoteError` if the given
remote does not exist
- `get_current_branch()` now raises a dedicated `DetachedHeadError` if the
repository is in a detached `HEAD` state
- `get_branch_upstream()` now raises a dedicated `NoUpstreamError` if the given
branch does not have an upstream configured

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- Make `get_local_repo()` handle remote names that start with a hyphen
- Add a `get_branch_upstream()` function

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- Do not accept repository names that end in "`.git`" with alternate casings

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- Support Python 3.10
- Export and document `GH_USER_RGX` and `GH_REPO_RGX`

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- `ghrepo` command: If a git invocation fails, exit with the same return code
as the subprocess
- Error messages from the `ghrepo` command are now prefixed with "ghrepo:"