tests/test-filecache.py.out

rust: move `filter_map_results` to public util

This is a useful general-purpose function.

It will be used in the next changesets.

basic:

* neither file exists
creating
* neither file still exists
* empty file x created
creating
* file x changed size
creating
* nothing changed with either file
* file x changed inode
creating
* empty file y created
creating
* file y changed size
creating
* file y changed inode
creating
* both files changed inode
creating

fakeuncacheable:

* neither file exists
creating
* neither file still exists
creating
* empty file x created
creating
* file x changed size
creating
* nothing changed with either file
creating
* file x changed inode
creating
* empty file y created
creating
* file y changed size
creating
* file y changed inode
creating
* both files changed inode
creating
repository tip rolled back to revision -1 (undo commit)
working directory now based on revision -1
repository tip rolled back to revision -1 (undo commit)
working directory now based on revision -1

setbeforeget:

* neither file exists
string set externally
* file x created
creating
string from function
* string set externally again
string 2 set externally
* file y created
creating
string from function

antiambiguity: