commands: be more uniform in an "hg update" error message
"can only specify one of -C/--clean, -c/--check, or -m/merge"
becomes
"can only specify one of -C/--clean, -c/--check, or -m/--merge"
{header}
<title>Error</title>
<description>Error</description>
<item>
<title>Error</title>
<description>{error|escape}</description>
<guid>https://mercurial-scm.org/#error</guid>
</item>
</channel>
</rss>