+# -DCOLLISION_CHECK if you believe that SHA1's
+# 1461501637330902918203684832716283019655932542976 hashes do not give you
+# enough guarantees about no collisions between objects ever hapenning.
+#
+# -DNSEC if you want git to care about sub-second file mtimes and ctimes.
+# Note that you need some new glibc (at least >2.2.4) for this, and it will
+# BREAK YOUR LOCAL DIFFS! show-diff and anything using it will likely randomly
+# break unless your underlying filesystem supports those sub-second times
+# (my ext3 doesn't).