add m4a and check if target file already exists

dotfiles/bin/.bin/compress-music

@@ -14,10 +14,10 @@ cd "$source"
 find . -type d -exec mkdir -p "$destination/{}" \;
 
 # copy existing files
-find . -type f -and \( -name '*.mp3' -or -name '*.ogg' -or -name '*.opus' \) -exec cp -a --reflink=always "{}" "$destination/{}" \;
+find . -type f -and \( -name '*.mp3' -or -name '*.m4a' -or -name '*.ogg' -or -name '*.opus' \) -exec cp -a --reflink=always "{}" "$destination/{}" \;
 
 # set +e because ffmpeg errors on .jpg, .txt, etc.
 set +e
 # compress with opus
-find . -type f -not -name '*.mp3' -not -name '*.ogg' -not -name '*.opus' | parallel --jobs $(($(nproc) - 1)) --eta --progress 'nice -n19 opusenc --bitrate 128 --music ""{}"" ""$destination/{.}.opus""'
+find . -type f -not -name '*.mp3' -not -name '*.m4a' -not -name '*.ogg' -not -name '*.opus' | parallel --jobs $(($(nproc) - 1)) --eta --progress 'test -f ""$destination/{.}.opus"" || nice -n19 opusenc --bitrate 128 --music ""{}"" ""$destination/{.}.opus""'
 #set -e