Fix incorrect object id hash function (go-gitea#30708)

Great thanks to @oliverpool for figuring out the problem and proposing a
fix.

Regression of go-gitea#28138

Incorrect hash causes the user's LFS files get all deleted when running
`doctor fix all`

(by the way, remove unused/non-standard comments)

Co-authored-by: Giteabot <teabot@gitea.io>

modules/git/object_format.go

@@ -33,7 +33,6 @@ type ObjectFormat interface {
 	ComputeHash(t ObjectType, content []byte) ObjectID
 }
 
-/* SHA1 Type */
 type Sha1ObjectFormatImpl struct{}
 
 var (
@@ -70,14 +69,10 @@ func (h Sha1ObjectFormatImpl) ComputeHash(t ObjectType, content []byte) ObjectID
 	_, _ = hasher.Write([]byte(" "))
 	_, _ = hasher.Write([]byte(strconv.FormatInt(int64(len(content)), 10)))
 	_, _ = hasher.Write([]byte{0})
-
-	// HashSum generates a SHA1 for the provided hash
-	var sha1 Sha1Hash
-	copy(sha1[:], hasher.Sum(nil))
-	return &sha1
+	_, _ = hasher.Write(content)
+	return h.MustID(hasher.Sum(nil))
 }
 
-/* SHA256 Type */
 type Sha256ObjectFormatImpl struct{}
 
 var (
@@ -116,11 +111,8 @@ func (h Sha256ObjectFormatImpl) ComputeHash(t ObjectType, content []byte) Object
 	_, _ = 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
+	_, _ = hasher.Write(content)
+	return h.MustID(hasher.Sum(nil))
 }
 
 var (

modules/git/object_id.go

@@ -16,7 +16,6 @@ type ObjectID interface {
 	Type() ObjectFormat
 }
 
-/* SHA1 */
 type Sha1Hash [20]byte
 
 func (h *Sha1Hash) String() string {
@@ -40,7 +39,6 @@ func MustIDFromString(hexHash string) ObjectID {
 	return id
 }
 
-/* SHA256 */
 type Sha256Hash [32]byte
 
 func (h *Sha256Hash) String() string {
@@ -54,7 +52,6 @@ func (h *Sha256Hash) IsZero() bool {
 func (h *Sha256Hash) RawValue() []byte { return h[:] }
 func (*Sha256Hash) Type() ObjectFormat { return Sha256ObjectFormat }
 
-/* utility */
 func NewIDFromString(hexHash string) (ObjectID, error) {
 	var theObjectFormat ObjectFormat
 	for _, objectFormat := range SupportedObjectFormats {

modules/git/object_id_test.go

@@ -18,4 +18,8 @@ func TestIsValidSHAPattern(t *testing.T) {
 	assert.False(t, h.IsValid("abc"))
 	assert.False(t, h.IsValid("123g"))
 	assert.False(t, h.IsValid("some random text"))
+	assert.Equal(t, "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391", ComputeBlobHash(Sha1ObjectFormat, nil).String())
+	assert.Equal(t, "2e65efe2a145dda7ee51d1741299f848e5bf752e", ComputeBlobHash(Sha1ObjectFormat, []byte("a")).String())
+	assert.Equal(t, "473a0f4c3be8a93681a267e3b1e9a7dcda1185436fe141f7749120a303721813", ComputeBlobHash(Sha256ObjectFormat, nil).String())
+	assert.Equal(t, "eb337bcee2061c5313c9a1392116b6c76039e9e30d71467ae359b36277e17dc7", ComputeBlobHash(Sha256ObjectFormat, []byte("a")).String())
 }