[dim] New spec proposal for mount index update

[Philippe Bergheaud]

dim [re]mount item|version dir
        Link all files from the mountpoint to the clone index.
OPTIONS
        -a | -o auto
                Automatically update the index to reflect the mount point 
contents.
        -o noauto
                Do not automatically update the index to reflect the mount 
point contents (default).
        -g | -o gitignore
                Honour .gitignore files when automatically updating the 
index.
        -o nogitignore
                Do not honour .gitignore files (default).