support creating patches from files in diff mode

pkg/commands/commit_file.go

@@ -2,6 +2,7 @@ package commands
 
 // CommitFile : A git commit file
 type CommitFile struct {
+	// Parent is the identifier of the parent object e.g. a commit SHA if this commit file is for a commit, or a stash entry ref like 'stash@{1}'
 	Parent        string
 	Name          string
 	DisplayString string