build/git-version-gen fallback to UNKNOWN breaks builds
@walters
Submitted by Colin Walters Link to original bug (#712768)
Description
I landed https://git.gnome.org/browse/jhbuild/commit/?id=40b70d75563f783cf41c403e7c797ab683803c52 into jhbuild a while ago, and it's quite a noticeable speedup to clone with --depth=1.
But build/git-version-gen will fail to "git describe" in this case, so it emits UNKNOWN into e.g. vapigen.pc.
This causes every VAPIGEN_CHECK(0.17.xxx) in various modules to fail.
Which in turn is really confusing if you're just trying to build seahorse and can't figure out why libsecret isn't building its vala API even though you have vala installed...
Anyways, I think we should fall back to the version that's specified in configure.ac.