The emerge option
autounmask features into the corresponding config files.
If the corresponding package.* is a directory, changes are written to the lexicographically last file in this directory. In order to prevent your manually managed files from being edited, you can create files just for the purpose of autounmask-write:
for d in /etc/portage/package.*; do touch $d/zzz_autounmask; done
Configuration files are protected so
autounmaskchanges will not be applied automaically.
After using the
--autounmask-writeoption, dispatch-conf can be used to review and merge the configuration changes.