[PATCH] Log, annotate and diff use an environment pager if available

[Bryan O'Sullivan]

David Soria Parra wrote:

> +  usepager;;
> +    If set to false, the pager is not used. True or False. Default is True.

This is a backwards incompatible change, and is not OK.

> -                self.ui.write(h)
> +                self.pager.write(h)

Whether or not a pager is being used should be hidden in the ui code.
It's bad layering to have it infect other sites at random.

> +

Don't add extra blank lines to code you're not changing.

> +    The pager is not used if the output is not longer than min_lines
> +    but instead prints the output to stdout.

The pager already contains logic to handle this kind of case, so there's
absolutely no reason to buffer output.

	<b