./MANIFEST.SKIP - many authors use this to list the files they have in their development directory which they don't want to package. Most distribution building processes will honour this list. They should really include MANIFEST.SKIP in their MANIFEST.SKIP so that it doesn't get distributed!
I disagree with that point. Not having/knowing the MANIFEST.SKIP can make it highly tedious to rebuild a distribution. I think that the .gitignore and MANIFEST.SKIP and other such ephemeral parts of distribution building should be distributed so that other people can easily rebuild a distribution file if they are running their own inhouse CPAN mirror for example.