Anchor links in feeds are not absolute

[dperelman]

• I have searched the issues (including closed ones) and believe that this is not a duplicate.
• I have searched the documentation and believe that my question is not covered.
• I am willing to lend a hand to help implement this feature.

Feature Request

I recently enabled the Markdown toc extension option to add permalinks to headers, but as it doesn't include the absolute URL in the link, it doesn't really do quite the right thing on pages other than the article page. I tried just hiding those links on the other pages with my theme, but that doesn't work for feeds as there's no CSS there. My RSS reader interpreted those links as going to http://myblog.example.com/#foo.

My workaround was to write this plugin which just rewrites all links in articles to #foo to the full absolute URL, which feels like a hack, but might be the right solution. Maybe it would be more proper to do this rewrite only when writing out a feed? But I didn't see a hook for a plugin to attach to that would affect only feeds.