Handle explicit version that matches current version

[krmcbride]

When I start a new project I often set the version to 0.1.0 (which you could argue is stupid, and probably comes from my Java background starting projects at 0.1.0-SNAPSHOT. Fair 'nuff). I expected to be able to run mversion 0.1.0 and just have the tool go through the normal tagging steps even though the version wasn't changing. Instead I got:

Failed updating:
Command failed:

which was puzzling. It took diving through the code to find that the invocation of git add was returning 1 since there were no modifications.

The simplest way to overcome this would be to stick a --allow-empty in there...but upon reflection, I think a better option would be

A) Enhance logging in such a way that I can tell I'm being stupid or...
B) Detect this condition and skip the commit step or...
C) ?

In the meantime I think I'll survive.