hg: add quietempty flag to _showstats if called with quietempty=True, suppress: 0 files updated, 0 files merged, 0 files removed, 0 files unresolved

patch: disable nobinary when HGPLAIN=1 The diff output without binaries is definitely great for interactive users - a binary patch is not meaningful for them. Although setting diff.nobinary flag can break the automation. Let's force full output for automation.