Version identification

[kaizu]

Determine the style of version naming.

The following documents gives the style for Python packages though it seems too complicated.
https://www.python.org/dev/peps/pep-0440/

The version style affects the following part:

https://github.com/ecell/ecell4-base/blob/master/ecell4/core/extras.hpp#L90-L101
https://github.com/ecell/ecell4-base/blob/master/ecell4/core/extras.cpp#L103-L168

[kaizu]

The project version is given here: https://github.com/ecell/ecell4-base/blob/master/CMakeLists.txt#L4

This also works as the version of Python pacage ecell4_base. Thus, it must be consistent with the style.

[kaizu]

The version scheme in PEP 440 is [N!]N(.N)*[{a|b|rc}N][.postN][.devN].

The current implementation only accepts N.N.N.

Here is a proposal: N.N.[dev]N

• No epoch
• At least two release numbers are required.
• Third release number is replaceable with a development release segment.

This accepts 1.0.dev2, but omit several styles such as 1.0.1.dev1, 1.0b2 and 1.0.post1.

[kaizu]

Or simply N.N[.devN]. Just two release numbers and one optional development segment.

[kaizu]

See also https://packaging.pypa.io/en/latest/version/

[kaizu]

Use N.N[.devN]: 1.0.dev1 -> 1.0.dev2 -> 1.0 -> 1.1.dev1 -> ...