* lib/fs: Add fakefs
This adds a new fake filesystem type. It's described rather extensively
in fakefs.go, but the main point is that it's for testing: when you want
to spin up a Syncthing and have a terabyte or two of random files that
can be synced somewhere, or an inifitely large filesystem to sync files
into.
It has pseudorandom properties such that data read from one fakefs can
be written into another fakefs and read back and it will look
consistent, without any of the data actually being stored.
To use:
<folder id="default" path="whatever" ...>
<filesystemType>fake</filesystemType>
This will create an empty fake filesystem. You can also specify that it
should be prefilled with files:
<folder id="default" path="whatever?size=2000000" ...>
<filesystemType>fake</filesystemType>
This will create a filesystem filled with 2TB of random data that can be
scanned and synced. There are more options, see fakefs.go.
Prefilled data is based on a deterministic seed, so you can index the
data and restart Syncthing and the index is still correct for all the
stored data.
