Swig code generation - git src vs tarball src

[John Ralls]

> On Mar 31, 2015, at 7:33 AM, Derek Atkins <warlord at mit.edu> wrote:
> 
> John Ralls <jralls at ceridwen.us> writes:
> 
>> I also think that it’s good that the build from a tarball based on a
>> random commit fails. Since that tarball doesn’t contain any version
>> information other than what’s in configure.ac, the resulting GnuCash
>> will look like the last release which could produce some confusing bug
>> reports.
> 
> Well, this isn't true.  You can "make dist" from any random commit and
> build from the resulting tarball.  But no, you cannot just tar up a
> random commit and build it.

Hmm, valid point. So in addition to rejiggering the "do we need swig" logic we should also change the versioning logic with VCS builds so that the version that goes on the splash screen and Help>About is the output of `git describe`. I suppose to be perfectly paranoid we should also disable make-dist for non-VCS builds, but perhaps that would be overdoing it.

Regards,
John Ralls