1 files changed, 25 insertions, 9 deletions

diff --git a/plumbing/format/index/encoder.go b/plumbing/format/index/encoder.go
index 00d4e7a..2c94d93 100644
--- a/plumbing/format/index/encoder.go
+++ b/plumbing/format/index/encoder.go
@@ -14,7 +14,7 @@ import (
 
 var (
 	// EncodeVersionSupported is the range of supported index versions
-	EncodeVersionSupported uint32 = 2
+	EncodeVersionSupported uint32 = 3
 
 	// ErrInvalidTimestamp is returned by Encode if a Index with a Entry with
 	// negative timestamp values
@@ -36,9 +36,9 @@ func NewEncoder(w io.Writer) *Encoder {
 
 // Encode writes the Index to the stream of the encoder.
 func (e *Encoder) Encode(idx *Index) error {
-	// TODO: support versions v3 and v4
+	// TODO: support v4
 	// TODO: support extensions
-	if idx.Version != EncodeVersionSupported {
+	if idx.Version > EncodeVersionSupported {
 		return ErrUnsupportedVersion
 	}
 
@@ -68,8 +68,12 @@ func (e *Encoder) encodeEntries(idx *Index) error {
 		if err := e.encodeEntry(entry); err != nil {
 			return err
 		}
+		entryLength := entryHeaderLength
+		if entry.IntentToAdd || entry.SkipWorktree {
+			entryLength += 2
+		}
 
-		wrote := entryHeaderLength + len(entry.Name)
+		wrote := entryLength + len(entry.Name)
 		if err := e.padEntry(wrote); err != nil {
 			return err
 		}
@@ -79,10 +83,6 @@ func (e *Encoder) encodeEntries(idx *Index) error {
 }
 
 func (e *Encoder) encodeEntry(entry *Entry) error {
-	if entry.IntentToAdd || entry.SkipWorktree {
-		return ErrUnsupportedVersion
-	}
-
 	sec, nsec, err := e.timeToUint32(&entry.CreatedAt)
 	if err != nil {
 		return err
@@ -110,9 +110,25 @@ func (e *Encoder) encodeEntry(entry *Entry) error {
 		entry.GID,
 		entry.Size,
 		entry.Hash[:],
-		flags,
 	}
 
+	flagsFlow := []interface{}{flags}
+
+	if entry.IntentToAdd || entry.SkipWorktree {
+		var extendedFlags uint16
+
+		if entry.IntentToAdd {
+			extendedFlags |= intentToAddMask
+		}
+		if entry.SkipWorktree {
+			extendedFlags |= skipWorkTreeMask
+		}
+
+		flagsFlow = []interface{}{flags | entryExtended, extendedFlags}
+	}
+
+	flow = append(flow, flagsFlow...)
+
 	if err := binary.Write(e.w, flow...); err != nil {
 		return err
 	}