commitctx: return "touched" status from _filecommit Instead of mutating a list passed in argument, we simply return the information from the `_filecommit` function. This make for a cleaner API and allow for richer information to be returned. That richer information will be used in the next commit to avoid duplicated computation. This is part of a larger refactoring/cleanup of the commitctx code to clarify and augment the logic gathering metadata useful for copy tracing. The current code is a tad too long and entangled to make such update easy. We start with easy and small cleanup. Differential Revision: https://phab.mercurial-scm.org/D8702