Permit selection of repo by index (rather than URL)

[bernd-wechner]

Currently, -l lists mirrors indexed, and -b just lists the first one and -a selects that first one.

It has happened to me that I want to use 2 or 3, for example, but am constrained to copy and paste the URL and us -c

IMHO, if there was an option akin to -l which prompted for and expected an int as input would then configure the selected one.

-c cannot take an int reliably, as the list of the last l run is not guaranteed to be the same when you run with c but you could bind this to -cl (or -lc) reliably, meaning change based on a list, or of course use a whole new option like C for interactive change which dumps then output of -l then prompts for an int to select one of them and once entered configures it.

Given the ease with which an int can be mis-typed or selected a confirmation step may be warranted, printing the URL selected and asking for confirmation.