When the update notifier is enabled and a new version was detected, show
a Homebrew upgrade notice if:
- the release was at least 24 hours ago; and
- the current `gh` binary is under the Homebrew prefix.
When gh was built from source, the version number will look something
like this since it's taken from `git describe`:
v1.4.0-34-g{SHA}
When compared as semver against `v1.4.0`, the latter version is falsely
reported as newer. This is because the output of `git describe` wasn't
meant to be interpreted as semver.
The solution is to translate the `git describe` string to faux-semver so
it can be safely compared with the version reported from the server.
Fixes this case:
A new release of gh is available: v1.4.0-41-g2f9e4cb1 → v1.4.0
https://github.com/cli/cli/releases/tag/v1.4.0
