[HEADS UP] Planned deprecation of portsnap

[Steve Wills]

We are planning to deprecate use of portsnap in ports.

The reasons are as follows (in no particular order):

* Portsnap doesn't support quarterly branches, even years after 
quarterly branches were created and changed to the default for non-HEAD 
packages.

* Portsnap doesn't seem to save disk space compared to svn or git, if 
you count the metadata (stored in /var/db/portsnap by default) and you 
do an apples-to-apples comparison of svn or git without history and 
ignoring possible ZFS compression. That is, you use "svn export" or git 
"clone --depth 1", you see this disk usage:

     342M    svnexport
     426M    git
     477M    portsnap

* Portsnap also doesn't work offline which git does. With git, you can 
also easily add the history by running "git pull --unshallow"

* This migration away from portsnap fits well with the planned migration 
to git.

* Also based on the patches we've seen in Bugzilla for some time, usage 
of portsnap causes folks to too easily accidentally submit patches to 
Bugzilla which don't apply easily.

* Since portsnap doesn't support quarterly branches, it often causes 
users to build on the wrong branch or end up with mismatched packages. 
That is, they install packages from quarterly via pkg, then want to 
customize so run portsnap and build from head, which can cause problems, 
as we often see. Even when this doesn't happen, it adds to 
troubleshooting to verify that it didn't.

We are aware people have gotten used to portsnap, but believe:

* People should be able to easily use svnlite in base or git from pkgs. 
(Very few people seem to actually use WITHOUT_SVNLITE).

* There is also the possibility of falling back to fetching a tar or zip 
from https://cgit-beta.freebsd.org/ports/ although this does make 
updating harder.

How it will be done, in order:

* Update poudriere to use svn by default. This is already done:

   https://github.com/freebsd/poudriere/pull/764
 
https://github.com/freebsd/poudriere/commit/bd68f30654e2a8e965fbdc09aad238c8bf5cdc10

* Update docs not to mention portsnap. This is already in progress:

   https://reviews.freebsd.org/D25800
   https://reviews.freebsd.org/D25801
   https://reviews.freebsd.org/D25803
   https://reviews.freebsd.org/D25805
   https://reviews.freebsd.org/D25808
   https://svnweb.freebsd.org/changeset/base/363798

   Many thanks to the folks who have worked and are working on this!

* Make WITHOUT_PORTSNAP default in base. Currently not certain when this 
will happen. May not happen before 13.0, but hopefully it will.

* Eventually, portsnap servers will see low enough usage they can be 
disabled.

We welcome any constructive feedback. All input would be heard, and if 
the plans need to be amended, we will come back to you with the amended 
plan in a couple of weeks. This process will take some time and 
hopefully won't be too disruptive to anyone's usual workflow.

Steve (with portmgr@ hat)