add back inode to directory special remote ContentIdentifier

add back inode to directory special remote ContentIdentifier

Directory special remotes with importtree=yes have changed to once more
take inodes into account. This will cause extra work when importing from a
directory on a FAT filesystem that changes inodes on every mount.

To avoid that extra work, set ignoreinodes=yes when initializing a new
directory special remote, or change the configuration of your existing
remote: git-annex enableremote foo ignoreinodes=yes

This will mean a one-time re-import of all contents from every directory
special remote due to the changed setting.

73df633a6215faa093e4a7524c6d328aa988aed1 thought
it was too unlikely that there would be modifications that the inode number
was needed to notice. That was probably right; it's very unlikely that a
file will get modified and end up with the same size and mtime as before.
But, what was not considered is that a program like NextCloud might write
two files with different content so closely together that they share the
mtime. The inode is necessary to detect that situation.

Sponsored-by: Max Thoursie on Patreon