Added README, noted a couple of ideas/TODOs

README.md

@@ -0,0 +1,2 @@
+Similar projects by other people:
+* https://github.com/mikeswain/cmdfs From what I understand, cmdfs needs to run the command on all files ahead of time in order to know the generated file size. It also seems to be more geared towards running a single command (e.g. convert ogg to mp3, or convert png to jpeg). I want to run different commands, and want them to be executed only when the file is accessed.

fs.py

@@ -203,4 +203,12 @@ def main(source, cache, mountpoint):
     FUSE(FilterFS(source, cache), mountpoint, nothreads=True, foreground=True, direct_io = True)
 
 if __name__ == '__main__':
-    main(sys.argv[1], sys.argv[2], sys.argv[3])
+    main(sys.argv[1], sys.argv[2], sys.argv[3])
+
+# TODO: an option to check that commands are signed with a trusted GPG key before executing them
+#       This would allow the user to run this on a filesystem containing a mix of trusted and
+#       untrusted files (e.g. tar -zxf untrusted-downloaded-file.tar.gz is dangerous). In order to
+#       prevent replay attacks, the signed data should include things like the path to the
+#       symlink-command (otherwise re-using that signed symlink-command in another location with
+#       different files could be used to change the semantics of the command), and/or the inputs
+#       (the command itself and the hash of the input files)

test.sh

@@ -56,4 +56,10 @@ else
   printf '\033[1;31mFailure\033[m\n'
   fusermount -u test/mnt || kill -KILL $pid
   exit 1
-fi
+fi
+
+# TODO: tests for ctime
+#       e.g. using https://serverfault.com/questions/520322/unix-ctime-how-to-keep-this-precious-information-in-backups-tar
+#       or https://www.halfgaar.net/backing-up-unix
+#       or simply find -print0 | xargs -0 stat
+#       Note that on ext4 we can't access this information without root permissions: https://unix.stackexchange.com/questions/50177/birth-is-empty-on-ext4