The file `.byebug_history` is generated when using the popular https://github.com/deivid-rodriguez/byebug gem for debugging in Ruby. It contains a list of commands the user has run while debugging, which should not be committed to the repository. The author of the gem agrees with this here: https://github.com/deivid-rodriguez/byebug/issues/204#issuecomment-178238302

I have copied this from the Rails gitignore here: https://github.com/github/gitignore/blob/f908e51bcf38ae5ede449c55189a7b25d8c507cc/Rails.gitignore#L45

This file is used moderately commonly to store environment variables locally. See Python.gitignore.

arcresu pointed out that `*.gem`, `*.rbc`, `.rvmrc` might not be at
the top level in a repository. Thus, remove leading slashes for these.

Perhaps this is a little pedantic, but without the initial / all
such matches within the repository get ignored, and without the
trailing slash files as well as directories of that name get ignored.
e.g. Specifying `tmp` and `test/tmp` without slashes is redundant, as
`tmp` already ignores `test/tmp`, as well as every other `tmp` and
`tmp/`.

(https://github.com/lsegal/yard)

Should be in Global/TextMate.gitignore