This is a partial revert of c435f06b308e52d7a5d2aad9eec98a1541832b47,
since it didn't actually fix the original problem with shallow clones.
It returns just a hash, not something we (currently) can extract as a
version string in the form things are expecting.
This one meets or exceeds the following requirements:
- Version is checked/updated for every build action when in the git repo.
Does not require the user to re- ./configure to get the correct version.
- Version is not updated automatically when using exported tarball source.
Avoids accidentally getting a wrong version from some other git repo in
a parent directory of the source, and allows setting the correct version
for distro package exports.
- Automatic updating can be manually suppressed.
For developers doing lots of change/rebuild cycles they don't plan to
release, when they don't want a full rebuild triggered for every commit,
and again for every change made immediately after a commit.
The version will still always be updated if they do a `make dist`.
- Does not require any manual updating of versions in the mainline git
repo for each release aside from normal tagging. The version is
recorded in one file only, that is automatically generated and will
never need to be committed.
- Does not require gnu-make features for the autoconf builds.
It does not currently:
- Keep a checksum of every source file in tarball releases to mangle the
version if people modify the tarball source. Responsible people can
manually update the version easily though in such cases.
The version.mk file is now only used by the VC project files. Once they
are updated to use the package_version file too, then it can be deleted
from the repository.
