When https://github.com/thoughtbot/administrate/pull/1718 was merged, it introduced a potential solution to /tmp/pids/.keep being unintentionally deleted. Unfortunately this didn't fix the issue and in fact seems to have made it worse.
I think the issue may have been solved already, and it was only surfacing again when moving between commits that included https://github.com/thoughtbot/administrate/commit/a0eeca682013a8ed357502f209eb47de7c5b1756 and those that didn't. I might be wrong though, but at least I was seeing it less now and I think that might have been the pattern.
The changes I'm proposing to gitignore are as currently generated in new Rails apps. Perhaps this will do the trick?