Add symlink method to util.opener.
Differences from os.symlink:
- the symlink name is relative to the opener base directory
- if a file with that name already exists, it's removed
- if necessary, parent directories are created
- if the system (OS or filesystem) doesn't support symlinks, a
regular file is created. Its contents are the symlink target.
adding b
rev offset length base linkrev nodeid p1 p2
0 0 3 0 0 1e88685f5dde 000000000000 000000000000