Bug 314425

The current code always regenerates the version.h file, but cmake ignores these changes and doesn't rebuild main.o. How to check:

- do a build on a clean git dir; you won't see the -dirty suffix
- echo blah >> Changelog
- run make
- the cmake's output says that the version ends with -dirty, but the binary is not rebuilt

A correct fix is apparently to use the add_custom_target command, perhaps as per [1]. In addition, I would prefer a solution without two custom .cmake files.

Finally, the current automation creates version.h in the source tree, not in the build tree. I have not changed this yet because I suspect the idea behind this is to allow for building the release tarballs from a local git checkout which was built previously. I prefer a solution where there's a #define in some .h file which is set to "4.x.z-git" in the non-release revisions, then updated to "4.x.z+1" by hand when doing the release, and immediately turned into "4.x.z+1-git" in a next commit to master. The result of `git describe --dirty` always takes precedence, but having a manually maintained fallback makes sure that there's a correct value even when someone e.g. fetches a zip file from some random web frontend for git. I suspect this is just a matter of personal preference, though.

Johannes, would you like a patch which does essentially what I just described? No promises on ETA, though.

[1] http://stackoverflow.com/questions/1435953/how-can-i-pass-git-sha1-to-compiler-as-definition-using-cmake