git conversion in progress

[Gerald Pfeifer]

On Mon, 13 Jan 2020, Joseph Myers wrote:
> In addition, once git.html is more complete (has the list of branches 
> added, at least) we need to update the GCC home page to link to the new 
> pages in place of those for SVN, redirect the old pages to the new ones, 
> and generally update references to SVN in wwwdocs and the GCC manuals.

I have removed all references to svnwrite.html and svn.html from our
own pages, added redirects to gitwrite.html and git.html, respectively,
and after svnwrite.html a few days ago now also removed svn.html.

There's some further changes I have in the queue, but the web site side
of things should be mostly converted now, modulo

 - more Git-specifics as you had pointed out,
 - bugs/reghunt.html which Jonathan offered to look into, and 
 - simtest-howto.html which looks a little dead to me.

Gerald