prune_pdf_digests removes the lines from the digest file
corresponding to a vector of source files.
     
    
    Usage
    prune_pdf_digests(files, root_dir = NULL)
 
     
    
    Arguments
- files
 
A character vector of paths to the source files to be removed.
 
- root_dir
 
The root directory of the HUGO project.
 
 
    
    Value
    The path to the digest file.
     
    
    Details
    Modifies the stored digest file to remove lines corresponding to selected
source files.