local_changes_only — whether there is a file for writing local configuration changes
local_changes_only = true
local_changes_only defaults to 'false'. If it is 'true', it must be defined and all changes are saved to the
local_changes_file. If it is 'false', changes are distributed as described below:
When replacing a value that has previously been set, if the file it was last set in is writable then the change is made in-place; the new option value replaces the old option value at the same location in the writable file.
If replacing a value that was last set in a read-only file or setting a value that was not set previously, then the change will go to the lexically first writable file in which the scope instance containing the change was defined.
local_changes_only is valid in the global scope.