When non-ascii characters appear in revision titles/summaries the `patch` and `diff` (to update) commands will fail on Windows systems. This often occurs due to “smart quotes” or "long-dash" characters being inserted into commit messages by editors on "user-friendly" operating systems like macOS.
This can be worked around by forcing all mercurial commands to use the global option `--encoding utf-8` which applies for any mercurial command. This option was [[ https://www.mercurial-scm.org/repo/hg/rev/a88e02081a88 | added in ~2006 ]] so this should work across all supported versions of mercurial.
Refs T13649