When extracting a folder name from the byte slices used as database
keys, bytes.IndexByte() is used to find and remove trailing 0 bytes.
In case the folder name is 64 bytes long, bytes.IndexByte() returns
-1. Before this change, syncthing crashed in this case with an
out-of-bounds slice access.
The commit fixes the problem and also introduces a test case which
checks for the presence of the bug.
- Bug fix - use .Errorf() instead of .Error():
Before this change, an error message for failed tests in files/set_test.go
wrongly tried to use format strings in a call to .Error()
- Change event constants to be of type EventType rather than untyped integers.
- Slightly relax the locking for registry cache lookups:
For read access to Discover.registry we only need to take a read lock.
- Some cosmetic fixes.
