We still haven't found a better way to rescan the Library than to fake an USBMS session, though (as the sdcard bind-mount trick may have some unwanted side-effects for people actually using their sd cards
).
(But on that note, you can now automate the "Connect" click either via a Nickel setting, or via FBInk. See
UNCaGED for an example of this very use-case).
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If you like doing things your way, you can also
hook into udev directly, instead of relying on the Nickel FIFO
.