govet: add appends analyzer

[Antonboom]

No description provided.

[ldez]

I understand why you added default values for enable and disable but it's not their default values: if you disable-all default passes are not the same as if you enable-all.

The default passes are unrelated to enable and disable.

[Antonboom]

@ldez

Any other idea how to highlight default values?

I was confused with empty list.
And for me it is more unobvious than different sets at disable and disable-all.

We can write

    # Disable all analyzers (not just those that are disabled by default).
    # Default: false
    disable-all: true