Look up a list of git attributes for path with extended options.
An array of num_attr entries that will have string pointers written into it for the values of the attributes. You should not modify or free the values that are written into this array (although of course, you should free the array itself if you allocated it).
The path inside the repo to check attributes. This does not have to exist, but if it does not, then it will be treated as a plain file (i.e. not a directory).
The number of attributes being looked up
An array of num_attr strings containing attribute names.
0 or an error code.