Add support for sha256 repositories (#23894)

Currently only SHA1 repositories are supported by Gitea. This adds
support for alternate SHA256 with the additional aim of easier support
for additional hash types in the future.

Fixes: #13794
Limited by: https://github.com/go-git/go-git/issues/899
Depend on: #28138

<img width="776" alt="图片" src="https://github.com/go-gitea/gitea/assets/81045/5448c9a7-608e-4341-a149-5dd0069c9447">

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>

1 files changed, 59 insertions, 6 deletions

diff --git a/modules/git/object_format.go b/modules/git/object_format.go
index 27771e7459..a056b20e8a 100644
--- a/modules/git/object_format.go
+++ b/modules/git/object_format.go
@@ -5,6 +5,7 @@ package git
 
 import (
 	"crypto/sha1"
+	"crypto/sha256"
 	"regexp"
 	"strconv"
 )
@@ -12,6 +13,9 @@ import (
 // sha1Pattern can be used to determine if a string is an valid sha
 var sha1Pattern = regexp.MustCompile(`^[0-9a-f]{4,40}$`)
 
+// sha256Pattern can be used to determine if a string is an valid sha
+var sha256Pattern = regexp.MustCompile(`^[0-9a-f]{4,64}$`)
+
 type ObjectFormat interface {
 	// Name returns the name of the object format
 	Name() string
@@ -29,11 +33,12 @@ type ObjectFormat interface {
 	ComputeHash(t ObjectType, content []byte) ObjectID
 }
 
+/* SHA1 Type */
 type Sha1ObjectFormatImpl struct{}
 
 var (
-	emptyObjectID = &Sha1Hash{}
-	emptyTree     = &Sha1Hash{
+	emptySha1ObjectID = &Sha1Hash{}
+	emptySha1Tree     = &Sha1Hash{
 		0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
 		0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04,
 	}
@@ -41,11 +46,11 @@ var (
 
 func (Sha1ObjectFormatImpl) Name() string { return "sha1" }
 func (Sha1ObjectFormatImpl) EmptyObjectID() ObjectID {
-	return emptyObjectID
+	return emptySha1ObjectID
 }
 
 func (Sha1ObjectFormatImpl) EmptyTree() ObjectID {
-	return emptyTree
+	return emptySha1Tree
 }
 func (Sha1ObjectFormatImpl) FullLength() int { return 40 }
 func (Sha1ObjectFormatImpl) IsValid(input string) bool {
@@ -72,11 +77,59 @@ func (h Sha1ObjectFormatImpl) ComputeHash(t ObjectType, content []byte) ObjectID
 	return &sha1
 }
 
-var Sha1ObjectFormat ObjectFormat = Sha1ObjectFormatImpl{}
+/* SHA256 Type */
+type Sha256ObjectFormatImpl struct{}
+
+var (
+	emptySha256ObjectID = &Sha256Hash{}
+	emptySha256Tree     = &Sha256Hash{
+		0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1,
+		0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5,
+		0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc,
+		0x53, 0x21,
+	}
+)
+
+func (Sha256ObjectFormatImpl) Name() string { return "sha256" }
+func (Sha256ObjectFormatImpl) EmptyObjectID() ObjectID {
+	return emptySha256ObjectID
+}
+
+func (Sha256ObjectFormatImpl) EmptyTree() ObjectID {
+	return emptySha256Tree
+}
+func (Sha256ObjectFormatImpl) FullLength() int { return 64 }
+func (Sha256ObjectFormatImpl) IsValid(input string) bool {
+	return sha256Pattern.MatchString(input)
+}
+
+func (Sha256ObjectFormatImpl) MustID(b []byte) ObjectID {
+	var id Sha256Hash
+	copy(id[0:32], b)
+	return &id
+}
+
+// ComputeHash compute the hash for a given ObjectType and content
+func (h Sha256ObjectFormatImpl) ComputeHash(t ObjectType, content []byte) ObjectID {
+	hasher := sha256.New()
+	_, _ = hasher.Write(t.Bytes())
+	_, _ = hasher.Write([]byte(" "))
+	_, _ = hasher.Write([]byte(strconv.FormatInt(int64(len(content)), 10)))
+	_, _ = hasher.Write([]byte{0})
+
+	// HashSum generates a SHA256 for the provided hash
+	var sha256 Sha1Hash
+	copy(sha256[:], hasher.Sum(nil))
+	return &sha256
+}
+
+var (
+	Sha1ObjectFormat   ObjectFormat = Sha1ObjectFormatImpl{}
+	Sha256ObjectFormat ObjectFormat = Sha256ObjectFormatImpl{}
+)
 
 var SupportedObjectFormats = []ObjectFormat{
 	Sha1ObjectFormat,
-	// TODO: add sha256
 }
 
 func ObjectFormatFromName(name string) ObjectFormat {