Homebrew's 'pin' command

If you don't know what homebrew is, then this isn't for you ...

Sometimes it's necessary to 'lock' a particular version or formula, so that it's not automagically updated during a routine brew update.

Apparently, though I'm not entirely sure why, the bash shell is one such formula that should be updated separately.

brew pin bash

Prevents any updates and can be reversed when needed with a simple brew unpin bash.