Log Message:
Update to 2.4.1:

This is a regularly-schedule bugfix release.

    amend: force editor only if old message is reused (issue3698)
    grep: don't search past the end of the searched string
    hooks: be even more forgiven of non-fd descriptors (issue3711)
    hooks: delay I/O redirection until we actually run a hook (issue3711)
    phases: fix missing "error" module import (issue3707)
    rebase: fix pull --rev options clashing with --rebase (issue3619)
    subrepo: add argument to "diff()" to pass "ui" of caller \ 
side (issue3712) (API)
    update: allow update to existing branches with invalid names (issue3710)
    util: make chunkbuffer non-quadratic on Windows