Implement semver for repository

[klimkin]

Considering adding a Conan package to CCI: conan-io/conan-center-index#4262
Could you use tags to implement semver on the repository, please? That would simplify version tracking in CCI.

[ianlancetaylor]

You should always use HEAD.

I don't see how semver would help here.

[klimkin]

semver tags are convenient for referring to particular release of the library. semver also helps making reproducible builds.

Using HEAD as versioning strategy is really a choice of a user, why to limit the choice?

[amery]

it's not that HEAD is not always the greatest. the point is to know what did one use in retrospective

[lanodan]

Not having versions means it's going to be hard for:

• packagers, they would have to carefully watch every commit, without themselves being maintainers of the library. (See https://archive.fosdem.org/2018/schedule/event/how_to_make_package_managers_cry/)
• application developers, it means it's harder to provide support and also likely to end up hard-depending on the latest HEAD should they want to use something new (instead of carefully guarding it)