use version number or git tag instead of date for version display

[Eric Deveaud]

Hello,

I noticed that smina use the build date as version number. see

[gensoft@f9480ac0e102 smina-20201209]$ smina --version
Smina Dec  9 2020.  Based on AutoDock Vina 1.1.2.

unfortunatly this will lead to some confusion if I rebuild smina with the same source tree later, version will obviously change

a more reproductible version tag wil be provided by using git commit short hash or a fixed version number that developer have to increment

best regards
Eric

[David Koes]

Done. b08c07c