rust: move `filter_map_results` to public util
This is a useful general-purpose function.
It will be used in the next changesets.
= Mercurial XXX =
== New Features ==
* There is a new internal merge tool called `internal:union-other-first`.
It works like `internal:union` but add other side on top of local.
== Default Format Change ==
These changes affect newly created repositories (or new clones) done with
Mercurial XXX.
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
== Miscellaneous ==
* pullbundle support no longer requires setting a server-side option,
providing a .hg/pullbundles.manifest according to the syntax specified in
'hg help -e clonebundles' is enough.