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.
1:016807e6fdaf
0:eb43f19ff115
016807e6fdaf tip
eb43f19ff115
eb43f19ff115+
eb43f19ff115
016807e6fdaf tip
merging file1
016807e6fdaf tip
016807e6fdaf tip
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