1 files changed, 88 insertions, 0 deletions
diff --git a/ref/name/component.go b/ref/name/component.go
new file mode 100644
index 00000000..f5adba46
--- /dev/null
+++ b/ref/name/component.go
@@ -0,0 +1,88 @@
+package refname
+
+import "strings"
+
+func checkRefnameComponent(name string, flags *int, sanitized *strings.Builder, fullName string) (int, error) {
+	var last byte
+
+	componentStart := sanitizedLen(sanitized)
+
+	for i := range len(name) {
+		ch := name[i]
+		disp := refnameDisposition(ch)
+
+		if sanitized != nil && disp != 1 {
+			sanitized.WriteByte(ch)
+		}
+
+		switch disp {
+		case 1:
+			goto out
+		case 2:
+			if last == '.' {
+				if sanitized != nil {
+					truncateBuilder(sanitized, sanitized.Len()-1)
+				} else {
+					return 0, &NameError{Name: fullName, Reason: "name contains '..'"}
+				}
+			}
+		case 3:
+			if last == '@' {
+				if sanitized != nil {
+					overwriteLastByte(sanitized, '-')
+				} else {
+					return 0, &NameError{Name: fullName, Reason: "name contains '@{'"}
+				}
+			}
+		case 4:
+			if sanitized != nil {
+				overwriteLastByte(sanitized, '-')
+			} else {
+				return 0, &NameError{Name: fullName, Reason: "name contains one forbidden character"}
+			}
+		case 5:
+			if *flags&refnameRefspecPattern == 0 {
+				if sanitized != nil {
+					overwriteLastByte(sanitized, '-')
+				} else {
+					return 0, &NameError{Name: fullName, Reason: "name contains '*'"}
+				}
+			}
+
+			*flags &^= refnameRefspecPattern
+		}
+
+		last = ch
+	}
+
+out:
+	componentLen := strings.IndexByte(name, '/')
+
+	if componentLen < 0 {
+		componentLen = len(name)
+	}
+
+	if componentLen == 0 {
+		return 0, nil
+	}
+
+	if name[0] == '.' {
+		if sanitized != nil {
+			overwriteBuilderAt(sanitized, componentStart, '-')
+		} else {
+			return 0, &NameError{Name: fullName, Reason: "component starts with '.'"}
+		}
+	}
+
+	if componentLen >= len(lockSuffix) && name[componentLen-len(lockSuffix):componentLen] == lockSuffix {
+		if sanitized == nil {
+			return 0, &NameError{Name: fullName, Reason: "component ends with .lock"}
+		}
+
+		for strings.HasSuffix(sanitized.String(), lockSuffix) {
+			truncateBuilder(sanitized, sanitized.Len()-len(lockSuffix))
+		}
+	}
+
+	return componentLen, nil
+}