If we’re talking specifically about executable scripts, here is #bash’s (libera.chat) factoid on the matter:

Don’t use extensions for your scripts. Scripts define new commands that you can run, and commands are generally not given extensions. Do you run ls.elf? Also: bash scripts are not sh scripts (so don’t use .sh) and the extension will only cause dependencies headaches if the script gets rewritten in another language. See http://www.talisman.org/~erlkonig/documents/commandname-extensions-considered-harmful

It’s for these reasons that I keep my executable scripts named without extensions (e.g. install).

I sometimes have non-executable scripts: they’re chmod -x, they don’t have a shebang, and they’re explicitly made for source-ing (e.g. library functions). For these, I give them an extension depending on what shell I wrote them for (and thus, what shell you need to use to source them), e.g. library.bash or library.zsh.

Quite a few times, sure. git bisect is a specific case of a more general technique – binary search fault localization – which comes in handy every once in a while (you can go a long while without needing it, but when you do need it, you’ll be thankful for it). If you can’t otherwise trace where in the code something is going wrong, bisect the code: comment or remove half of it out, see if it reproduces (therefore localizing it to either the removed or the remaining half), and repeat. If you’re working with some software that’s breaking on your config after a major version bump, bisect your config. Don’t have an idea what introduced a bug into your branch? git bisect.