bug#7989: 23.2.91; How do I update "local" autoloads?

[Chong Yidong]

> *File M-x update-file-autoloads puts autoloads into.
> A `.el' file can set this in its local variables section to make its
> autoloads go somewhere else.
>
> First, there's something missing here: it doesn't explain that if the
> value is a plain file name, then a directory is automatically
> prepended (and that's the source directory, which seems odd).

I've clarified the docstring, thanks.

> 2. I could set generated-autoload-file before running
> update-directory-autoloads, but I have no idea whether this would have
> a deleterious effect on, for example, ELPA. In a nutshell, why would I
> want to set a global variable for a one-off operation?

ELPA isn't affected, because it explicitly binds generated-autoload-file
to an absolute filename before running update-directory-autoloads.

I agree that the interactive interfaces to update-file-autoloads and
update-directory-autoloads are not very friendly.  Maybe when they are
called interactively, they should prompt for generated-autoload-file.