Is there a clever way to underline a heading?

Question

This isn't a particularly important, but it's something I've been curious about for a while.

I write a lot of documentation using rST (Sphinx). This is how you write a heading:

My Awesome Heading
==================

Lorem ipsum dolor...

I'm wondering if there's a clever way in vim to do that underline, rather than just rapidly pressing the equals key a dozen times.

Answer 1

" underline current line
yypVr=

Answer 2

:t.|s/./=/g

One keypress shorter than Barton's solution. ;)

Answer 3

Try

yyp
:s/./=/g

This copies and pastes the current line, then substitutes '=' for each character.

You can wrap this a macro or set up a function within .vimrc