github.com/spf13/viper's recent releases introduced a semantic
change in some public API such as viper.IsSet(), which have
broken some of our flags checks. Instead of checking whether
users have changed a flag's default value we should rely on such
defaults and adjust runtime behaviour accordingly. In order to do
so, it's important that we pick sane defaults for all our flags.
The --pruning flag and configuration option now allow for a
fake custom strategy. When users elect custom, then the
pruning-{keep,snapshot}-every options are interpreted and
parsed; else they're ignored.
Zero is pruning-{keep,snapshot}-every default value. When
users choose to set a custom pruning strategy they are
signalling that they want more fine-grainted control, therefore
it's legitimate to expect them to know what they are doing and
enter valid values for both options.
Ref #5964
e8cedf243f