refactor patch code

pkg/commands/patch/patch_line.go

@@ -0,0 +1,30 @@
+package patch
+
+import "github.com/samber/lo"
+
+type PatchLineKind int
+
+const (
+	PATCH_HEADER PatchLineKind = iota
+	HUNK_HEADER
+	ADDITION
+	DELETION
+	CONTEXT
+	NEWLINE_MESSAGE
+)
+
+type PatchLine struct {
+	Kind    PatchLineKind
+	Content string // something like '+ hello' (note the first character is not removed)
+}
+
+func (self *PatchLine) isChange() bool {
+	return self.Kind == ADDITION || self.Kind == DELETION
+}
+
+// Returns the number of lines in the given slice that have one of the given kinds
+func nLinesWithKind(lines []*PatchLine, kinds []PatchLineKind) int {
+	return lo.CountBy(lines, func(line *PatchLine) bool {
+		return lo.Contains(kinds, line.Kind)
+	})
+}