all: run gofumpt (#652)

* all: run gofumpt

https://github.com/mvdan/gofumpt

The main appeal for me here is that my (and many other peoples')
editors run this on save, so doing a single diff here
keeps other diffs minimal.

* .github/workflows: add gofumpt checker

plugin/yaml/yaml.go

@@ -107,7 +107,7 @@ func (p *plugin) checkPerm(filename string) error {
 		return nil
 	}
 
-	if fi.Mode().Perm()&0077 != 0 {
+	if fi.Mode().Perm()&0o077 != 0 {
 		return fmt.Errorf("%v's perm is too open", filename)
 	}
 

plugin/yaml/yaml_test.go

@@ -54,5 +54,4 @@ func TestYamlDecode(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to unmarshal yaml: %v", err)
 	}
-
 }