Second PR for #47.

Previously, we were setting CFBundleVersion to the output of git describe --tags (vX.Y.Z or vX.Y.Z-N-gHASH for preview builds).

To support Sparkle, and potentially to avoid a breakage with macOS failing to update an installed LaunchDaemon when it can't parse CFBundleVersion, we'll conform the string to the specification.

Given that:

You can include more integers but the system ignores them.

We set CFBundleVersion to a value of the form X.Y.Z[.N] where N is the number of commits since the X.Y.Z tag (omitted if 0)

Sparkle did previously allow you to supply a manual version comparator, but it was deprecated to help require CFBundleVersion start with X.Y.Z sparkle-project/Sparkle#2585

That issue recommends instead putting marketing version information in CFBundleShortVersionString, but that actually has even stricter requirements: https://developer.apple.com/documentation/bundleresources/information-property-list/cfbundleshortversionstring

Though not documented, from testing & reading the Sparkle source, I discovered that X.Y.Z.N+1 will be deemed a later version than X.Y.Z.N, which is what we'll do for the preview stream of auto-updates.

For non-preview builds (i.e. builds on a tag), both version strings will be X.Y.Z.

Since we're no longer including the commit hash in a version string, we instead embed it separately in the Info.plist so we can continue to display it in the UI: