chgserver: more explicit about sensitive environ variables Environment variables like HGUSER, HGEDITOR, HGEDITFROM should not trigger a new chgserver. This patch uses a whitelist for environ variables starting with "HG" to reduce the number of servers. I have went through `grep -o "[\"']HG[A-Z_0-9]*['\"]" -hR . | sort -u` so the list should be up-to-date.