bug#37538: [PATCH] Add docstring for `tags-complete-tags-table-file'.

[Hong Xu]

Eli Zaretskii <eliz@gnu.org> writes:
> How about the below:
>
>   (defun tags-complete-tags-table-file (string predicate what)
>     "Complete STRING from file names in the current tags table.
>   PREDICATE, if non-nil is a function to filter possible matches:
>   if it returns nil, the match is ignored.  If PREDICATE is nil,
>   every possible match is acceptable.
>   WHAT is a flag specifying the type of completion: t means `all-completions'
>   operation, any other value means `try-completions' operation.
>
>   This function serves as COLLECTION argument to `completing-read',
>   see the Info node `(elisp) Programmed Completion' for more detailed
>   description of the arguments."

Looks good to me. Thanks.