2016-02-29 - auto-generating revision and tags

most project deal with providing build-reversion and tags to build manually. there is however an interesting trick to automate getting revision number in cmake. while not perfect (one must rebuild twice when ninja is used)), it is reasonably useful to put into a real project.

i've introduced the concept for getting revision ID (git's commit hash) and list (!!) of tags in production system, we're currently working on. it works like a charm. from now on, whenever we get logs from testers, we can clearly see which version of our software was used, even if there are human-errors in description fields. it turned out to be quite a time savior, in some cases.