Adjust object format interface (#28469)

- Remove `ObjectFormatID`
- Remove function `ObjectFormatFromID`.
- Use `Sha1ObjectFormat` directly but not a pointer because it's an
empty struct.
- Store `ObjectFormatName` in `repository` struct

modules/git/object_format.go

@@ -5,26 +5,17 @@ package git
 
 import (
 	"crypto/sha1"
-	"fmt"
 	"regexp"
-	"strings"
-)
-
-type ObjectFormatID int
-
-const (
-	Sha1 ObjectFormatID = iota
 )
 
 // sha1Pattern can be used to determine if a string is an valid sha
 var sha1Pattern = regexp.MustCompile(`^[0-9a-f]{4,40}$`)
 
 type ObjectFormat interface {
-	ID() ObjectFormatID
-	String() string
-
-	// Empty is the hash of empty git
-	Empty() ObjectID
+	// Name returns the name of the object format
+	Name() string
+	// EmptyObjectID creates a new empty ObjectID from an object format hash name
+	EmptyObjectID() ObjectID
 	// EmptyTree is the hash of an empty tree
 	EmptyTree() ObjectID
 	// FullLength is the length of the hash's hex string
@@ -35,67 +26,71 @@ type ObjectFormat interface {
 	MustIDFromString(s string) ObjectID
 	NewID(b []byte) (ObjectID, error)
 	NewIDFromString(s string) (ObjectID, error)
-	NewEmptyID() ObjectID
 
 	NewHasher() HasherInterface
 }
 
-type Sha1ObjectFormat struct{}
+type Sha1ObjectFormatImpl struct{}
 
-func (*Sha1ObjectFormat) ID() ObjectFormatID { return Sha1 }
-func (*Sha1ObjectFormat) String() string     { return "sha1" }
-func (*Sha1ObjectFormat) Empty() ObjectID    { return &Sha1Hash{} }
-func (*Sha1ObjectFormat) EmptyTree() ObjectID {
-	return &Sha1Hash{
+var (
+	emptyObjectID = &Sha1Hash{}
+	emptyTree     = &Sha1Hash{
 		0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
 		0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04,
 	}
+)
+
+func (Sha1ObjectFormatImpl) Name() string { return "sha1" }
+func (Sha1ObjectFormatImpl) EmptyObjectID() ObjectID {
+	return emptyObjectID
 }
-func (*Sha1ObjectFormat) FullLength() int { return 40 }
-func (*Sha1ObjectFormat) IsValid(input string) bool {
+
+func (Sha1ObjectFormatImpl) EmptyTree() ObjectID {
+	return emptyTree
+}
+func (Sha1ObjectFormatImpl) FullLength() int { return 40 }
+func (Sha1ObjectFormatImpl) IsValid(input string) bool {
 	return sha1Pattern.MatchString(input)
 }
 
-func (*Sha1ObjectFormat) MustID(b []byte) ObjectID {
+func (Sha1ObjectFormatImpl) MustID(b []byte) ObjectID {
 	var id Sha1Hash
 	copy(id[0:20], b)
 	return &id
 }
 
-func (h *Sha1ObjectFormat) MustIDFromString(s string) ObjectID {
+func (h Sha1ObjectFormatImpl) MustIDFromString(s string) ObjectID {
 	return MustIDFromString(h, s)
 }
 
-func (h *Sha1ObjectFormat) NewID(b []byte) (ObjectID, error) {
+func (h Sha1ObjectFormatImpl) NewID(b []byte) (ObjectID, error) {
 	return IDFromRaw(h, b)
 }
 
-func (h *Sha1ObjectFormat) NewIDFromString(s string) (ObjectID, error) {
+func (h Sha1ObjectFormatImpl) NewIDFromString(s string) (ObjectID, error) {
 	return genericIDFromString(h, s)
 }
 
-func (*Sha1ObjectFormat) NewEmptyID() ObjectID {
-	return NewSha1()
-}
-
-func (h *Sha1ObjectFormat) NewHasher() HasherInterface {
+func (h Sha1ObjectFormatImpl) NewHasher() HasherInterface {
 	return &Sha1Hasher{sha1.New()}
 }
 
-func ObjectFormatFromID(id ObjectFormatID) ObjectFormat {
-	switch id {
-	case Sha1:
-		return &Sha1ObjectFormat{}
-	}
+var Sha1ObjectFormat ObjectFormat = Sha1ObjectFormatImpl{}
 
+var SupportedObjectFormats = []ObjectFormat{
+	Sha1ObjectFormat,
+	// TODO: add sha256
+}
+
+func ObjectFormatFromName(name string) ObjectFormat {
+	for _, objectFormat := range SupportedObjectFormats {
+		if name == objectFormat.Name() {
+			return objectFormat
+		}
+	}
 	return nil
 }
 
-func ObjectFormatFromString(hash string) (ObjectFormat, error) {
-	switch strings.ToLower(hash) {
-	case "sha1":
-		return &Sha1ObjectFormat{}, nil
-	}
-
-	return nil, fmt.Errorf("unknown hash type: %s", hash)
+func IsValidObjectFormat(name string) bool {
+	return ObjectFormatFromName(name) != nil
 }