Furthermore:
1. Cleans configs received, migrates them as we receive them.
2. Clears indexes of devices we no longer share the folder with
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3478
This slightly changes the interface used for committing configuration
changes. The two parts are now:
- VerifyConfiguration, which runs synchronously and locked, and can
abort the config change. These callbacks shouldn't *do* anything
apart from looking at the config changes and saying yes or no. No
change from previously.
- CommitConfiguration, which runs asynchronously (one goroutine per
call) *after* replacing the config and releasing any locks. Returning
false from these methods sets the "requires restart" flag, which now
lives in the config.Wrapper.
This should be deadlock free as the CommitConfiguration calls can take
as long as they like and can wait for locks to be released when they
need to tweak things. I think this should be safe compared to before as
the CommitConfiguration calls were always made from a random background
goroutine (typically one from the HTTP server), so it was always
concurrent with everything else anyway.
Hence the CommitResponse type is gone, instead you get an error back on
verification failure only, and need to explicitly check
w.RequiresRestart() afterwards if you care.
As an added bonus this fixes a bug where we would reset the "requires
restart" indicator if a config that did not require restart was saved,
even if we already were in the requires-restart state.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3386
