switch to fork of go-git

vendor/github.com/jesseduffield/go-git/v5/plumbing/hash.go

@@ -0,0 +1,83 @@
+package plumbing
+
+import (
+	"bytes"
+	"crypto/sha1"
+	"encoding/hex"
+	"hash"
+	"sort"
+	"strconv"
+)
+
+// Hash SHA1 hashed content
+type Hash [20]byte
+
+// ZeroHash is Hash with value zero
+var ZeroHash Hash
+
+// ComputeHash compute the hash for a given ObjectType and content
+func ComputeHash(t ObjectType, content []byte) Hash {
+	h := NewHasher(t, int64(len(content)))
+	h.Write(content)
+	return h.Sum()
+}
+
+// NewHash return a new Hash from a hexadecimal hash representation
+func NewHash(s string) Hash {
+	b, _ := hex.DecodeString(s)
+
+	var h Hash
+	copy(h[:], b)
+
+	return h
+}
+
+func (h Hash) IsZero() bool {
+	var empty Hash
+	return h == empty
+}
+
+func (h Hash) String() string {
+	return hex.EncodeToString(h[:])
+}
+
+type Hasher struct {
+	hash.Hash
+}
+
+func NewHasher(t ObjectType, size int64) Hasher {
+	h := Hasher{sha1.New()}
+	h.Write(t.Bytes())
+	h.Write([]byte(" "))
+	h.Write([]byte(strconv.FormatInt(size, 10)))
+	h.Write([]byte{0})
+	return h
+}
+
+func (h Hasher) Sum() (hash Hash) {
+	copy(hash[:], h.Hash.Sum(nil))
+	return
+}
+
+// HashesSort sorts a slice of Hashes in increasing order.
+func HashesSort(a []Hash) {
+	sort.Sort(HashSlice(a))
+}
+
+// HashSlice attaches the methods of sort.Interface to []Hash, sorting in
+// increasing order.
+type HashSlice []Hash
+
+func (p HashSlice) Len() int           { return len(p) }
+func (p HashSlice) Less(i, j int) bool { return bytes.Compare(p[i][:], p[j][:]) < 0 }
+func (p HashSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+// IsHash returns true if the given string is a valid hash.
+func IsHash(s string) bool {
+	if len(s) != 40 {
+		return false
+	}
+
+	_, err := hex.DecodeString(s)
+	return err == nil
+}