git-annex-5.20150406: doc/forum/two_lines_back_to_remote__63__.mdwn

`git annex map` generates a diagram roughly like this:

    +------+    +-------+
    |laptop| -> |usbdisk|
    |      | <- |       |
    |      | <- |       |
    +------+    +-------+

Why are there *two* lines back from the disk to the laptop?