Remove all matching index entries.
If you provide a callback function, it will be invoked on each matching item in the index immediately before it is removed. Return 0 to remove the item, > 0 to skip the item, and < 0 to abort the scan.
notification callback for each removed path (also gets index of matching pathspec entry); can be NULL; return 0 to add, >0 to skip, < 0 to abort scan.
payload passed through to callback function
0 on success, negative callback return value, or error code