[or-cvs] [githax/master] Finish most of the note about transition to git. Others should poke at it now until it looks reasonable.

[Nick Mathewson]

Author: Nick Mathewson <nickm at torproject.org>
Date: Thu, 23 Apr 2009 19:28:57 -0400
Subject: Finish most of the note about transition to git.  Others should poke at it now until it looks reasonable.

---
 doc/Transition-note.txt |  118 ++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 106 insertions(+), 12 deletions(-)

diff --git a/doc/Transition-note.txt b/doc/Transition-note.txt
index a358875..565a16b 100644
--- a/doc/Transition-note.txt
+++ b/doc/Transition-note.txt
@@ -35,10 +35,14 @@ Git.  Here are some things that Git gets us:
   messes up the repository with half-finished, half-tested stuff, but
   _not_ checking in partial work.
 
-  Good branch support lets us check in uncompleted work into its own
-  topic-specific branch .
+  Good branch support lets us check in each uncompleted batch of work
+  into its own topic-specific branch, and collaborate on uncompleted
+  work, without risking the stability of the main branch until we have
+  something finished and tested to check in.  This way, we won't waste
+  so much energy shipping versions with not-wholly-completed features,
+  or pulling out things that seemed like a good idea at first.
 
-- Better support for distributed development.
+- Better support for distributed collaboration.
 
   Frequently, I'd like to test out a few versions change on a few
   computers (or a few dozen) before committing it to the main Tor
@@ -49,26 +53,116 @@ Git.  Here are some things that Git gets us:
   computers, and with other people around the Internet, without having
   to manage patches by hand.
 
+  This isn't just for single-user patching, by the way.  A DVCS like
+  git makes it easy for several people to all work on a branch
+  together, either hosting it themselves, or on a site like github, or
+  everybody having their own copy that they share with one another.
+
 - Better support for offline development.
 
+  I do lots of my work in parks and on airplanes.  The ability to
+  commit offline and check in my commits later keeps me from messing
+  up the tree with huge omnibus patches, like I used to do on
+  Mixminion.
+
+- Better support for security fix development.
+
+  This is a big one for me.  Sometimes, when we get wind of a big
+  security vulnerability, I need to come up with a patch that I can
+  test as much as possible without revealing that the vulnerability
+  exists.  With the Debian OpenSSL problem the other year, I found
+  myself slinging versioned patch files around, begging directory
+  operators to test them, making patches on the patches, and otherwise
+  slowing down the bugfix by not being able to use our regular tools
+  to version it.
+
 - Cryptographic confirmation of repository integrity.
 
-  If someone were to compromise the machine where our SVN repository is
-  hosted, they could probably make changes in the software and its
-  history without getting caught.  With Git, every version is identified
-  by its digest, so it is much harder to damage a compromised repository
-  without being detected.
+  If someone were to compromise the machine where our SVN repository
+  is hosted, they could probably make changes in the software and its
+  history without getting caught.  With Git, every version is
+  identified by its digest, so it is much harder to damage a
+  compromised repository without being detected.  Knowing the hash of
+  a single version is sufficient verify the entire history up to that
+  version.  Git supports pgp-signed tags, so we can start signing tags
+  inside our repository in the same way we currently sign
+  distributions.
+
+WHAT ARE THE RISKS, AND HOW WILL YOU MITIGATE THEM?
+
+RISK: We may completely scew up the transition and break everything.
+
+  I hope not.  We've already got a procedure that I've tested out with
+  the repositories for Thandy, the Java Torctl, and Puppetor.
+  Obviously, too, we'll be backing up the repository before we start.
+
+RISK: This will totally mess up translations.
+
+  We're not moving the website.  We're not moving anything now except
+  for the Tor program itself; see above.
+
+RISK: People may go gonzo with the ability to do distributed development,
+  and not tell anybody about their patches.
 
+  This is a problem we've already got.  People sometimes write patches
+  without talking to the development community first, and so we wind up
+  with well-written but ultimately useless things, like patches that
+  reimplement features that 0.2.1.x already has against ancient
+  versions of the 0.1.2.x branch.
 
+  Development is already distributed.  What a DVCS enables is better
+  collaboration between distributed devlopers.
 
+RISK: Git may be too hard for people to understand.
+
+  Check out "how does this affect me?" below.  For the operations most
+  people already doing (get latest version from trunk; apply curent
+  changs to latest version;), Git is about as hard as subversion.  The
+  operations that are trickier are ones Subversion doesn't support at
+  all, like working with multiple remote repositories, rebasing
+  branches, or doing complex merges.
+
+RISK: People may go into bike-shed mode, and decide to start a massive
+  flamewar about whether we shouldn't really be using Mercurial or
+  Bazaar or Monotone or Darcs or such.
+
+  There's not much I can do here, other than remind people about the
+  story of the bike shed.  [http://www.bikeshed.com/]
 
 HOW DOES THIS AFFECT ME?
 
-== If you download Tor from the download page
+== If you download Tor as a package
+
+  It doesn't affect you at all, except inasmuch as it helps us develop
+  Tor more effectively and get you better work faster.
+
+== If you have been tracking Tor from subversion, but not changing it
+
+  Instead of checking out the repository using "svn checkout", you'll
+  clone it out with "git clone".  Instead of saying "svn update" to
+  see the latest version, you'll say "git pull".
+
+== If you have been writing patches for Tor against subversion, and
+   mailing them in.
+
+  As above, you'll need to use git to get the latest development
+  version, not subversion.  If you do your work on a local git branch,
+  though, you have a better ability to make sure that your patches
+  form a logical sequence, and that they apply cleanly against the
+  latest Tor before you send them in.
+
+  Of course, you can still just do your patches against a working copy,
+  use "git diff" to generate a patch, and email it in.  Just because
+  you have support for local branches and versioning doesn't mean you
+  need to use it.
+
+WHAT SHOULD I DO NOW?
 
-It doesn't affect you at all, except inasmuch as it helps us develop Tor
-more effectively and get you better work faster.
+It wouldn't be a bad time to learn Git.
 
-== If
+[INSERT LINKS TO GOOD READINGS HERE.]
 
 
+yrs,
+-- 
+Nick Mathewson
-- 
1.5.6.5