CODING: update guidance on using the git tree

We don't really need a "Danger Will Robinson"-style warning at this
point.

Also update the browsing URL to use TLS (https://).

Change-Id: I102b8bd8a8c91c68d6d6383ea146a0cb57b8d571
Reviewed-on: https://gerrit.openafs.org/15716
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>

CODING

@@ -204,13 +204,10 @@ way to do this?)
 GIT Usage
 =========
 
-*WARNING* *WARNING* *WARNING* *WARNING* *WARNING* *WARNING* *WARNING*
+With the broad continuous integration coverage provided by buildbot
-The Git tree may not always have code which can currently be built.
+and the current code review policy for changes entering master, it's
-While every effort is made to keep the head of the tree buildable,
+generally expected that the development branch will be buildable and
-you may at any time find yourself between commits and hence have a tree
+functional at any given time.
-which does not build, or worse, causes more serious problems!
-
-Do not use the Git tree unless you know what you're doing.
 
 Git checkouts do not include files generated by autoconf. You can
 run regen.sh (at the top level) to create these files. You will need
@@ -219,7 +216,7 @@ to have autoconf and automake installed on your system.
 Summary
 -------
 
-Browse:  http://git.openafs.org/
+Browse:  https://git.openafs.org/
 Clone:   git clone git://git.openafs.org/openafs.git
 
 Step-by-step