"git gui" would complain at launch if the local version of Git was
"1.5.4.2.dirty". Loosen the regular expression to look for either
"-dirty" or ".dirty", thus eliminating spurious warnings.
Signed-off-by: Wincent Colaiuta <win@wincent.com> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>