don't re-write the large asset file if it exists

cmd/git-media-clean.go

@@ -25,14 +25,55 @@ func main() {
 	written, _ := io.Copy(writer, os.Stdin)
 	sha := hex.EncodeToString(sha1Hash.Sum(nil))
 
-	meta := &gitmedia.LargeAsset{
+	asset := &gitmedia.LargeAsset{
 		MediaType: "application/vnd.github.large-asset",
 		Size:      written,
 		MD5:       hex.EncodeToString(md5Hash.Sum(nil)),
 		SHA1:      sha,
 	}
 
-	mediafile := gitmedia.LocalMediaPath(sha)
+	output := ChooseWriter(asset, tmp)
+	defer output.Close()
+
+	output.Write([]byte(fmt.Sprintf("# %d\n", len(gitmedia.MediaWarning))))
+	output.Write(gitmedia.MediaWarning)
+	enc := json.NewEncoder(output)
+	enc.Encode(asset)
+}
+
+func ChooseWriter(asset *gitmedia.LargeAsset, tmp *os.File) io.WriteCloser {
+	mediafile := gitmedia.LocalMediaPath(asset.SHA1)
+	if stat, _ := os.Stat(mediafile); stat == nil {
+		return NewGitMediaCleanWriter(asset, tmp)
+	} else {
+		return NewGitMediaExistingWriter(asset, tmp)
+	}
+}
+
+type GitMediaExistingWriter struct {
+	tempfile *os.File
+	writer   io.Writer
+}
+
+func NewGitMediaExistingWriter(asset *gitmedia.LargeAsset, tmp *os.File) io.WriteCloser {
+	return &GitMediaExistingWriter{tmp, os.Stdout}
+}
+
+func (w *GitMediaExistingWriter) Write(buf []byte) (int, error) {
+	return w.writer.Write(buf)
+}
+
+func (w *GitMediaExistingWriter) Close() error {
+	return os.Remove(w.tempfile.Name())
+}
+
+type GitMediaCleanWriter struct {
+	metafile *os.File
+	*GitMediaExistingWriter
+}
+
+func NewGitMediaCleanWriter(asset *gitmedia.LargeAsset, tmp *os.File) io.WriteCloser {
+	mediafile := gitmedia.LocalMediaPath(asset.SHA1)
 	metafile := mediafile + ".json"
 
 	if err := os.Rename(tmp.Name(), mediafile); err != nil {
@@ -46,12 +87,17 @@ func main() {
 		panic(err)
 	}
 
-	defer file.Close()
-	defer func() { os.Remove(tmp.Name()) }()
-
-	writer = io.MultiWriter(os.Stdout, file)
-	writer.Write([]byte(fmt.Sprintf("# %d\n", len(gitmedia.MediaWarning))))
-	writer.Write(gitmedia.MediaWarning)
-	enc := json.NewEncoder(writer)
-	enc.Encode(meta)
+	return &GitMediaCleanWriter{
+		metafile:               file,
+		GitMediaExistingWriter: &GitMediaExistingWriter{tmp, io.MultiWriter(os.Stdout, file)},
+	}
+}
+
+func (w *GitMediaCleanWriter) Write(buf []byte) (int, error) {
+	return w.writer.Write(buf)
+}
+
+func (w *GitMediaCleanWriter) Close() error {
+	w.GitMediaExistingWriter.Close()
+	return w.metafile.Close()
 }