FR: Add added(), deleted(), clean(), ignored(), conflicted() and resolved() fileset functions

[AngelEzquerra]

Is your feature request related to a problem? Please describe.
When creating a colocated jujutsu repo on an existing repo that has some untracked but not gitignored files, they are added to the working directory revision automatically. In order to untrack them all in one single command, it'd be great to have a way to refer to all of them using a fileset such as "added()". This exists in mercurial and it is quite handy. In addition to that it would make sense some of the other missing fileset functions, such as clean(), ignored(), etc. It would also be nice to have filesets to find conflicted files.

Describe the solution you'd like
Adding those missing functions (e.g. added() would return the list of files added on a revision, etc)

Describe alternatives you've considered
I don't think there are any.

[arxanas]

@martinvonz remarked on Discord:

i see. ignored() is my least favorite of those because it's specific to the working copy
so it requires asking the working copy (not the working-copy commit) for data [...]

To expand: Most of the filesets here are meant to be evaluated within the commit with respect to its parents, but ignored() is unlike added()/deleted()/clean()/conflicted()/resolved():

• The most intuitive meaning of ignored() involves checking the working copy (not even the working copy commit), and it doesn't/can't depend on the commit content.
  • Tangential: There's probably some valid and consistent interpretation of ignored() as "files that are in a commit and would also be ignored according to the .gitignore files within the same commit", but that sounds a lot less useful/intuitive.
• The same applies for a hypothetical untracked() fileset, etc.
• If we indeed want to add a function with different semantics than the rest, then we should be mindful about the interface and documentation.