We have the invalid bit to indicate that a file isn't good. That's enough for remote devices. For ourselves, it would be good to know sometimes why the file isn't good - because it's an unsupported type, because it matches an ignore pattern, or because we detected the data is bad and we need to rescan it.
Or, and this is the main future reason for the PR, because it's a change detected on a receive only device. We will want something like the invalid flag for those changes, but marking them as invalid today means the scanner will rehash them. Hence something more fine grained is required.
This introduces a LocalFlags fields to the FileInfo where we can stash things that we care about locally. For example,
FlagLocalUnsupported = 1 << 0 // The kind is unsupported, e.g. symlinks on Windows
FlagLocalIgnored = 1 << 1 // Matches local ignore patterns
FlagLocalMustRescan = 1 << 2 // Doesn't match content on disk, must be rechecked fully
The LocalFlags fields isn't sent over the wire; instead the Invalid attribute is calculated based on the flags at index sending time. It's on the FileInfo anyway because that's what we serialize to database etc.
The actual Invalid flag should after this just be considered when building the global state and figuring out availability for remote devices. It is not used for local file index entries.
To optimize WithNeed, which is called for the local device whenever an index
update is received. No tracking for remote devices to conserve db space, as
WithNeed is only queried for completion.
This adds a couple of utilities for transporting databases in JSON and a
test to load a database and verify a couple of invalid bits. The test
itself is quite pointless at the moment, but it lays the groundwork for
testing the migration of this data in the next step (after the invalid
bit should be changed to local flags for local files).
When that happens we need to have a database in the old format already
there in order to be able to test the migration.
When dropping delta index IDs due to upgrade, only drop our local one.
Previously, when dropping all of them, we would trigger a full send in
both directions on first connect after upgrade. Then the other side
would upgrade, doing the same thing. Net effect is full index data gets
sent twice in both directions.
With this change we just drop our local ID, meaning we will send our
full index on first connect after upgrade. When the other side upgrades,
they will do the same. This is a bit less cruel.
We're going to need the db.Instance to keep some state, and for that to
work we need the same one passed around everywhere. Hence this moves the
leveldb-specific file opening stuff into the db package and exports the
dbInstance type.
