AccessType -> FSHook.AccessType
Register outputs immediately rather than at command end
rcrOutputs is Map to Reason
TODO
Buildsome/Main -> Main
Oops: We have a bug in our identification of outputs (attempted
outputs that already existed are NOT command outputs) so until that is
fixed, we must not try to delete identified outputs. Just warn about
them, and fail the build, instead.
FSHook: Print nice error messages about bug-induced exceptions to help
debug them properly
Split fs_override: open to openr and openw. Add ReadWriteMode vs
WriteMode to openw. Change HELLO message to have PROTOCOL1: prefix.
fs_override.c: PREFIX -> ENVVARS_PREFIX. HELLO -> PROTOCOL_HELLO