[PATCH v2 2/2] log: allow users to follow a file

Awesome! Your patches work great over here. I'm so glad, I had not tried
to implement this myself :)

> For commits before the file has been renamed (i.e. that appear later in
> the log list) we change the file path in the links from the log to point
> to the old name; this means that links to commits always limit by the
> path known to that commit.  If we didn't do this we would need to walk
> down the log diff'ing every commit whenever we want to show a commit.
> The drawback is that the "Log" link in the top bar of such a page links
> to the log limited by the old name, so it will only show pre-rename
> commits.  I consider this a reasonable trade-off since the "Back" button
> still works and the log matches the path displayed in the top bar.

I also think this is reasonable. When running into this issue, you
usually already know what you are doing, so one might be surprised but
not lost.

- Ren?