Add a command to delete all but one file in *noninteractive* without using *prefer*. --keep-only-one

[oxalorg]

Most of the other duplication tool removers allow combining options like delete and noprompt to preserve the first file in each set of duplicates and delete the rest without prompting the user. Thus I think that it is a very common use case.

Currently combining --delete with --noninteractive causes to save ALL files if there is no preferred path match.

Something like --keep-only-one along with both --delete and --noninteractive should delete all but the first match if the preferred list is empty.

EDIT: I'm trying to work on, will post here if I have some progres. In the meanwhile Thoughts would be appreciated. Created a pull request.

[ssokolow]

I did think about this, but I'm a bit concerned about blindly asking a duplicate-finder to "delete one" without any cue as to which should be deleted.