debugfsinfo: print fstype information Since we have osutil.getfstype, it'll be handy if "debugfsinfo" prints it.

util: enable hardlink for copyfile This patch removes the global variable "allowhardlinks" that disables hardlink in all cases, so hardlink gets enabled if the filesystem type is whitelisted. Third party extensions wanting to enable hardlink support unconditionally can replace "_hardlinkfswhitelist.__contains__".

hghave: add a check about whitelisted filesystem that supports hardlink This is needed for the test added by the next patch.