[Python-Dev] New workflow change: Welcome to blurb

[Larry Hastings]

One minor but ongoing problem we've had in CPython core development has 
been the mess of updating Misc/NEWS.  Day-to-day developers may have a 
conflict if they lose a push race, which means a little editing.  You'll 
have a similar, if slightly worse, problem when cherry-picking a fix 
between versions.  Worst of all used to be the manual merges necessary 
after cutting a release--this was the bane of a CPython release 
manager's existence.  (Though the new git-based workflow may have 
obviated the worst of this.)

The real problem is that we have one central file that everybody 
continually edits in a haphazard way.  We aren't actually editing the 
same information, we aren't actually changing the same lines. But our 
revision control systems and diff algorithms don't understand the 
structure of Misc/NEWS and so they get confused. And for what? It's not 
like there's a tremendous benefit to having this central file everyone's 
fighting over.

We've been talking about addressing this for years.  Fixing this was one 
of the goals of the new workflow.  And finally, as of right now, the 
future is here.  Ladies and gentlemen, I present: blurb.

    https://github.com/python/core-workflow/tree/master/blurb


blurb is an interactive command-line tool that helps you write Misc/NEWS 
entries.  You simply run blurb from anywhere inside a CPython repo.  
blurb runs an editor for you with a template open. You fill in these 
three pieces of information:

  * the bugs.python.org or "bpo" issue number,
  * what "section" of Misc/NEWS this entry should go in (by uncommenting
    the correct line), and
  * the text of the Misc/NEWS entry, in ReST format.

You save and exit and you're done.  blurb even stages the Misc/NEWS 
entry in git for you!


Behind the scenes, blurb writes your information here:

    Misc/NEWS.d/next/<section-name>/<filename>

The "<section-name>" is the name of the section in Misc/NEWS where your 
entry should go.  <filename> contains the current date and time, the bpo 
number, and a nonce to prevent collisions.

These "next" files get merged together into a single aggregate .rst file 
by the release manager when cutting a release (using "blurb release").  
One nice feature of this approach: when you cherry-pick a change, its 
Misc/NEWS entry in "next" gets cherry-picked along with it.


One important change: Misc/NEWS will no longer be checked in. It'll 
still be present in CPython tarballs; it will be generated by the 
release manager as part of cutting a release.  But as a repository of 
information, it's been superseded by the various blurb data files.  And 
by regenerating it from data files, we ensure that we'll never ever have 
a Misc/NEWS conflict ever again!

The plan is to leave Misc/NEWS in the CPython repo for maybe another 
week, to let the current crop of PRs get merged.  But new work should 
switch to using blurb immediately.


You can install blurb from pip:

    % pip3.6 install blurb

In fact--please do!


//arry/
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