Shortcut for '--merge-sensitive'

In the course of adding auditing ability to the Subversion command line
client, we've assumed the existence of the '--merge-sensitive' switch,
and some single character shortcut for it. A couple of suggestions have
come up for what the shortcut should be, so I'm presenting them here,
and letting folks bikeshed about it. The two that have been propsed
are: '-g' and '-M'.

I prefer '-g', mainly because it is lowercase and '-M' could be confused
with '-m'.

-Hyrum