record hunk start position

Author: beyang

diff/diff.go

@@ -45,6 +45,11 @@ type Hunk struct {
 
 	Section string // optional section heading
 
+	// 0-indexed line offset in unified file diff (including section headers);
+	// this is only set when Hunks are read from entire file diff (i.e., when ReadAllHunks is called)
+	// This accounts for hunk headers, too, so the StartPosition of the first hunk will be 1.
+	StartPosition int
+
 	Body []byte // hunk body (lines prefixed with '-', '+', or ' ')
 }
 

diff/parse.go

@@ -492,13 +492,17 @@ func normalizeHeader(header string) (string, string, error) {
 // reported.
 func (r *HunksReader) ReadAllHunks() ([]*Hunk, error) {
 	var hunks []*Hunk
+	linesRead := 0
 	for {
 		hunk, err := r.ReadHunk()
 		if err == io.EOF {
 			return hunks, nil
 		}
 		if hunk != nil {
+			linesRead++ // account for the hunk header line
+			hunk.StartPosition = linesRead
 			hunks = append(hunks, hunk)
+			linesRead += bytes.Count(hunk.Body, []byte{'\n'})
 		}
 		if err != nil {
 			return hunks, err