fix getting version from tarball

[BenTheElder]

the docker tags are mangled, and the tarball has the version file matching what we'd get from a local source build

fixes #3714

cc @dims @aojea @stmcginnis

[BenTheElder]

For release builds, there's no additional metadata, so the docker tag and version file are the same.

The version file represents the binary version, what you'd get from kubectl version etc.
The docker tag file represents the mangled form that isn't quite semver because of docker tag character-set limitations.

[aojea]

I can see both are the same

$ more kubernetes/server/bin/kube-apiserver.docker_tag
v1.32.0-alpha.0.156_983875b2f5bf64
aojea@aojea:~/src/tmp$ more kubernetes/version
v1.32.0-alpha.0.156+983875b2f5bf64

the version seems more correct though

/lgtm

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[stmcginnis]

/lgtm

[BenTheElder]

The + is valid semver while _ is not, which is why we only use the _ for the image tags in Kubernetes, it doesn't parse.

[aojea]

The + is valid semver while _ is not, which is why we only use the _ for the image tags in Kubernetes, it doesn't parse.

Missed that details