OS X's GNU grep does not support -P/--perl-regexp.
We use a basic RE instead, and simplify the pattern slightly by
replacing '+' with '*' so it can be more easily expressed using a basic
RE. The important part of pattern, checking for a SHA-1 has suffix in
the successful PUT/MOVE operations, remains the same. Also, a-z instead
of a-f was an obvious mistake in the original RE. Here are samples of
what we want to match: