Provision for forcing argument as `numeric`

[jigarius]

The problem

• Say, a user is in /a/2/b/c/d and they want to go to 2.
• Typing gup 2 will take them to /a/2/b, i.e. 2 levels up.
• There should be a way to force the argument as alphanumeric / dirname

Proposed solution

• Create a switch which will force gup to treat the argument as a dirname

[jigarius]

Running gup with a number, say, gup 5 now does the following:

• If an ancestor directory named 5 exists, you go there.
• If an ancestor directory named 5 doesn't exists, you go 5 levels up.

However, you can force 5 to be treated as a number with the --number or -n flag.
Running gup -n 5 takes you 5 levels up, even if an ancestor directory named 5 exists.