'partition' function

[sobjornstad]

This would be a shortcut tool, which I anticipate working something like this. To replace:

$ dr fd t Signif 1 | dr winnow t Lucid 1 | dr act find
13 matches: [1, 2, 3, ...]
$ dr fd t Signif 1 | dr winnow -v t Lucid 1 | dr act find
32 matches: [100, 101, 102, ...]

With:

$ dr fd t Signif 1 | dr partition t Lucid 1
t Lucid 1 = 13 matches: [1, 2, 3, ...]
-v t Lucid 1 = 32 matches: [100, 101, 102, ...]

Ideally you could specify a non-boolean criterion too somehow, or two alternatives, but I'm not sure how that'd interact with comma-separated header fields.