Add path to cache hash

Without the `st_dev` the `st_ino` is no longer enough to uniquely
identify a file. A disadvantage of including the mtime in the hash is
that changed previews don't overwrite the old cache path so the cached
grows faster.

We use the path to the file to uniquely identify a device. We
concatenate it with the `st_ino` which ensures that replacing a file is
not enough to cause a collision. This is hashed to create the cache
path. Every time we check whether a preview is cached we verify that the
file being preview is as old or older than the cached preview.

The only differences from the original scheme are the algorithm (SHA-512
now), accepting previews of with the same mtime as the original file and
including the inode identifier in the hash.

0 files changed, 0 insertions, 0 deletions