gopages: link to source broken if used with absolute -base

[flesser]

When generating a page with gopages -internal -base "https://my-domain/docs/"
the links to the source code (e.g. of an func or Type) are broken since that absolute base url is prepended with a ./ in the generated href like this <a href="./https://my-domain/docs/src/pkg/foo/bar.go.html#L42">Foo</a>

Expected:

a href without relative prefix ./ like this: <a href="https://my-domain/docs/src/pkg/foo/bar.go.html#L42">Foo</a>

[JohnStarich]

Thank you @flesser for opening. I haven't had a change to try to reproduce / fix, but I'm open to a PR if you're up for it!

[JohnStarich]

As a work-around, it should be possible to set the base URL as an absolute path only. e.g. -base /docs