Subdirectories do not increment parent directory's link count

[dsheets]

When a subdirectory is created, the parent directory's link count increases by 1 (for ..) on typical POSIX-like file systems. Using 27c4078, a directory's link count remains 2 when subdirectories are created:

# mkdir foo
# stat foo
  File: ‘foo’
  Size: 4096        Blocks: 1          IO Block: 4096   directory
Device: 29h/41d Inode: 8           Links: 2
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 1970-01-01 01:00:00.000000000 +0100
Modify: 1970-01-01 01:00:00.000000000 +0100
Change: 1970-01-01 01:00:00.000000000 +0100
 Birth: -
# mkdir foo/bar
# stat foo
  File: ‘foo’
  Size: 4096        Blocks: 1          IO Block: 4096   directory
Device: 29h/41d Inode: 8           Links: 2
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 1970-01-01 01:00:00.000000000 +0100
Modify: 1970-01-01 01:00:00.000000000 +0100
Change: 1970-01-01 01:00:00.000000000 +0100
 Birth: -

While many POSIX foreign file systems do not obey directory link count invariants, it can be useful for programs (e.g. find) which perform many directory traversals.