When computing the build version (i.e. no BUILD_VERSION was specified in cmake command), cmake first checks for a VERSION_CURRENT file, and if one does not exist, then computes the version from git metadata with calc_release_version.py.

This could be problematic for users building from source. E.g. if they build from source and generate a VERSION_CURRENT file, future builds won't regenerate VERSION_CURRENT.

Perhaps the logic should be:

• attempt to compute the version with calc_release_version.py first
  • if it is greater than VERSION_CURRENT, overwrite it
  • if it is equal, do nothing
  • if it is less, return an error
• if calc_release_version.py fails to run (e.g. python/git are not installed) then fall back to VERSION_CURRENT

For a real life scenario where this almost happened, homebrew caches the repository files of installed packages. If installing from --HEAD, the VERSION_CURRENT file would be generated on first install, but not regenerated on upgrades. (But currently this is not an issue, because passing BUILD_VERSION was the proposed solution in CDRIVER-3410).