Allows for configuring the UID and GID Syncthing runs as in the container. Uses su-exec from the Alpine repos to accomplish this. Addition of su-exec results in <2MB increase in image size.
This makes the environment variables easier to read/change.
Also expand the list so it's not inline, more readable that way.
The new architecture syntax for snapcraft allows specifying both the building architecture and the running architecture of the snap, so if we specify the build-on architecture as the host architecture and the run-on architecture as the target architecture, then snapcraft shouldn't need to install any cross-compilers, etc.
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.
It's pretty much the GitHub standard, says the obvious, and does it
better than our old one which was a little bit rambling.
Intentionally just doing it instead of discussing it, in the hope of
avoiding trolling. So sue me.
