* snapshot: support for periodic checkpointing of snapshots in progress
For each snapshot that takes longer than 45 minutes, we trigger
internal cancellation, save the manifest and restart the snapshot
at which point all files will be cached.
This helps ensure the property that no file or directory objects
in the repository remain unreachable from a snapshot root for more than
one hour, which is important from GC perspective.
* nit: unified spelling 'cancelled' => 'canceled'
* This is 99% mechanical:
Extracted repo.Repository interface that only exposes high-level object and manifest management methods, but not blob nor content management.
Renamed old *repo.Repository to *repo.DirectRepository
Reviewed codebase to only depend on repo.Repository as much as possible, but added way for low-level CLI commands to use DirectRepository.
* PR fixes
The hostname/username are now persisted when connecting to repository
in a local config file.
This prevents weird behavior changes when hostname is suddenly changed,
such as when moving between networks.
repo.Repository will now expose Hostname/Username properties which
are always guarnateed to be set, and are used throughout.
Removed --hostname/--username overrides when taking snapshot et.al.
This is mostly mechanical and changes how loggers are instantiated.
Logger is now associated with a context, passed around all methods,
(most methods had ctx, but had to add it in a few missing places).
By default Kopia does not produce any logs, but it can be overridden,
either locally for a nested context, by calling
ctx = logging.WithLogger(ctx, newLoggerFunc)
To override logs globally, call logging.SetDefaultLogger(newLoggerFunc)
This refactoring allowed removing dependency from Kopia repo
and go-logging library (the CLI still uses it, though).
It is now also possible to have all test methods emit logs using
t.Logf() so that they show up in failure reports, which should make
debugging of test failures suck less.
This cleans up the code a lot and removes many ugly hacks.
The performance is pretty reasonable and with separate metadata cache it's likely to stay that way.
Also introduced strongly typed content.ID and manifest.ID (instead of string)
This aligns identifiers across all layers of repository:
blob.ID
content.ID
object.ID
manifest.ID
