switch to semantic versioning

[prjemian]

Following apstools, spec2nexus would benefit by switching to use of semantic versioning rather than its current scheme of calendar-based versioning.

Note:

• higher numbered versions will always be selected in preference to lower numbered, even if the lower number is newer
• conda packaging (using versioneer) is based on git tags, not GitHub releases

• It takes a couple steps to upgrade a conda installation from a calendar-based release (such as 2017.901.4) to a newer semantic version, such as 2.0.0.

  1. add a conda-meta/pinned declaration for spec2nexus< 2000 in the conda environment
  2. conda update -c prjemian spec2nexus (should change to latest semantic version number, such as 2.0.0)

What to do with existing tags?

There are too many calendar-based releases and tags to remove them from GitHub. Leave them. They will be a nuisance and a constant reminder about this.

How to update?

Even if the 2019. releases and conda packages are removed, it may still be necessary to uninstall and reinstall spec2nexus* to effect an update:

1. conda uninstall -y spec2nexus
2. conda install -c prjemian "spec2nexus< 2000"

What will be the next version number?

Accepting that the CalVer releases started (effectively) the 1.0 series. The change in scan numbering (due to multiple, identical scan numbers in a single file) was API-breaking, thus began the (effectively) 2.0 series. This change in versioning scheme does not break the current API, so the next version will be 2.1.0.

[prjemian]

The only work to be done here is to use semver during the next release process. Renaming the milestone was the first step.

[prjemian]

released