change default strftime format for better portability
On some systems, such as Solaris and HP-UX, "%c" format
give output without the leading zero on the single-digit
month-day.
%%% should show a removed and b added
A b
R a
reverting...
%%% should show b unknown and a back to normal
? b
merging a
%%% should show foo-b
foo-b
%%% should show a removed and b added
A b
R a
reverting...
%%% should show b unknown and a marked modified (merged)
? b
%%% should show foo-b
foo-b