feat(rule): add FooterEnum rule

Author: muthukrishnan24

config/default.go

@@ -146,6 +146,13 @@ func Default() *lint.Config {
 				Severity: lint.SeverityError,
 				Argument: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ/,",
 			},
+
+			// Footer Enum Rule
+			(&rule.FooterEnumRule{}).Name(): {
+				Enabled:  false,
+				Severity: lint.SeverityError,
+				Argument: []interface{}{},
+			},
 		},
 	}
 	return def

internal/registry/registry.go

@@ -51,9 +51,9 @@ func newRegistry() *registry {
 		&rule.BodyMinLenRule{}, &rule.BodyMaxLenRule{},
 		&rule.FooterMinLenRule{}, &rule.FooterMaxLenRule{},
 		&rule.HeadMaxLenRule{}, &rule.HeadMinLenRule{},
-		&rule.TypeEnumRule{}, &rule.ScopeEnumRule{},
-
 		&rule.BodyMaxLineLenRule{}, &rule.FooterMaxLineLenRule{},
+
+		&rule.TypeEnumRule{}, &rule.ScopeEnumRule{}, &rule.FooterEnumRule{},
 		&rule.TypeCharsetRule{}, &rule.ScopeCharsetRule{},
 
 		&rule.TypeMaxLenRule{}, &rule.ScopeMaxLenRule{}, &rule.DescriptionMaxLenRule{},

rule/enum.go

@@ -84,6 +84,43 @@ func (r *TypeEnumRule) Apply(arg interface{}, flags map[string]interface{}) erro
 	return nil
 }
 
+// FooterEnumRule to validate footer tokens
+type FooterEnumRule struct {
+	Tokens []string
+}
+
+// Name return name of the rule
+func (r *FooterEnumRule) Name() string { return "footer-enum" }
+
+// Validate validates FooterEnumRule
+func (r *FooterEnumRule) Validate(msg *lint.Commit) ([]string, bool) {
+	msgs := []string{}
+
+	for _, note := range msg.Notes() {
+		isFound := search(r.Tokens, note.Token())
+		if !isFound {
+			errMsg := fmt.Sprintf("footer token '%s' is not allowed, you can use one of %v", note.Token(), r.Tokens)
+			msgs = append(msgs, errMsg)
+		}
+	}
+
+	if len(msgs) == 0 {
+		return nil, true
+	}
+	return msgs, false
+}
+
+// Apply sets the needed argument for the rule
+func (r *FooterEnumRule) Apply(arg interface{}, flags map[string]interface{}) error {
+	err := setStringArrArg(&r.Tokens, arg)
+	if err != nil {
+		return errInvalidArg(r.Name(), err)
+	}
+	// sorting the string elements for binary search
+	sort.Strings(r.Tokens)
+	return nil
+}
+
 func search(arr []string, toFind string) bool {
 	ind := sort.Search(len(arr), func(i int) bool {
 		return arr[i] >= toFind