Text consistency: command-line, command line, commandline

[kinow]

We have several variations. It would be nice to choose the preferred way, and update our CONTRIBUTING.md file (or Wiki, or README.md, etc.). We may have to also notify translators so the translated text follows that too, if that makes sense in the target language.

[Mackenzie-OO7]

Hi @kinow I'd like to work on this issue. Have we decided on the preferred way?
Although they can be used interchangeably, "command-line" is usually used to refer to the interface, while "command line" is usually used when referring to options, commands and arguments on the command line.