If you want the package from the repository to contain the man page, you need to open a bug report against the package: go to < and click "Add new bug".
`man whipper` does not open the man page after you ran `make` in `man/` because `man` doesn't search the current directory for man pages. To do that, you need the `--local-file` (`-l` for short) option of `man`: `man --local-file whipper.1`.