cli: major refactoring of how CLI commands are registered
The goal is to eliminate flags as global variables to allow for better
testing. Each command and subcommand and most sets of flags are now
their own struct with 'setup()' methods that attached the flags or
subcommand to the provided parent.
This change is 94.3% mechanical, but is fully organic and hand-made.
* introduced cli.appServices interface which provides the environment in which commands run
* remove auto-maintenance global flag
* removed globals in memory_tracking.go
* removed globals from cli_progress.go
* removed globals from the update_check.go
* moved configPath into TheApp
* removed remaining globals from config.go
* refactored logfile to get rid of global variables
* removed 'app' global variable
* linter fixes
* fixed password_*.go build
* fixed BSD build
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.
