• Have you test the code?
• Have you check that the existing tests are passing?
• The destination branch is develop?

This addresses #72
With minimal refactoring, I minimized the changes needed to support parameters more easily, and thereby minimized the amount of code needed to add this feature. These changes are backwards compatible except for error cases; in particular, flags may now appear before or after options, whereas before they could only appear before options. For example, prior to this patch, this would cause an error:

immortalctl -1 stop service

but worse, this would kill all services:

immortalctl stop -1 service

With this patch, arguments and flags are parsed correctly: all flags appear before arguments, which is required for flags.Parse() to work correctly. The positional logic has been largely removed, making adding flags far easier. All of the positional logic has been moved to a single block of 10 lines, making the flow easier to understand, and less fragile. Validation of arguments has been collected and simplified.

This is still not a completely correct use of the flags library, and there remain vestigual anachronisms, such as around line 45, but a fully idiomatic refactoring would be a larger and more disruptive patch.