source: trunk/doc/procedures @ 20856

This file contains a description of the process developers should go
through to get changes into the source tree.  Although it discusses
the use of CVS, it is not a CVS tutorial; read the CVS info pages
(available in M-x info in emacs on Athena) for a general introduction
to CVS.  Areas covered in this file are:

  Checking out a working directory
  Preparing changes for review
  Reviewing changes
  Early checkins
  Third-party sources

You should use cvs from the gnu locker with the source repository.
People without write access to the repository can use "cvs -u" (a
local modification to CVS) to access the repository without making
read locks.  If you do not have write access to the repository and you
want to submit a change, follow the guidelines below up and including
sending mail to source-reviewers, and note in your mail that your
reviewer should check in the change because you cannot do so.

Checking out a working directory
--------------------------------

Set CVSROOT to "/afs/dev.mit.edu/source/repository" before trying to
check out a working directory.

The entire source tree is very large.  You can check it out with "cvs
co -P all", but in almost all cases this would be a big waste of space.
Simply check out a subdirectory of the source tree with a command like
"cvs co -P athena/bin/olc".

CVS knows nothing about AFS permissions, so all directories created
will have the same permissions as their parent.  It is generally
safest to do your checkouts in a private area of the filesystem.

You should use the -P option for checkout because the source tree
contains some historical directories (now empty) which will conflict
with builds.

Preparing changes for review
----------------------------

Changes to the doc hierarchy do not typically need to be reviewed;
notification is typically good enough, since no software will break as
a result of changes to the source tree documentation.

For changes to other parts of the tree, you should perform the
following steps while preparing your changes for review:

  1. Do a "cvs update" in your working directory to merge in changes
     other people may have made.  (You can do "cvs -n update" if you
     want to see what needs to be merged in without actually doing the
     merge.)

  2. Be sure to test your changes.

  3. Make sure your changes are made in reviewable chunks to the
     greatest extent possible.  If you have many changes to make of
     several different types, prepare one patch for each type of
     change; in particular, if you have some cosmetic changes to make
     and some functional fixes to make, submit them as two different
     patches if they add up to a significant number of changes.  This
     requirement creates more work for the submitter, but it greatly
     increases the effectiveness of the review process.

  4. Use "cvs diff -u -N" piped to a file to prepare your changes.  (Do
     not cut and paste diffs from an xterm; your tabs will be
     converted to spaces.)  If your change involves reindentation of
     code, you may want to also use the "-w" flag to diff.  If you
     find that your change is clearer when presented as a context diff
     ("-c" instead of "-u"), feel free to submit it that way.

  5. Look over your diffs.  Make sure you haven't been sloppy about
     spacing, punctuation, and naming, and that you have tried to
     conform to the guidelines in the file "standards" in this
     directory

  6. Send your diffs, along with a clear description of the change you
     are making, to source-reviewers@mit.edu.  If the diffs are very
     large (more than 50K), put the changes somewhere world-readable
     (unless the source code in question is restricted) and mail a
     pointer.

  7. If you do not have write access to the source tree and submitted
     your diff using the -w flag, submit it again without the -w flag
     so that the full patch can be checked in by someone with write
     access.

Ideally, at least one person will respond to your mail within a day or
two, either expressing concerns or signing onto your change.  You
should wait at least one day for people to voice their objections.  If
you receive objections or requests for further information from staff
members, you must either satisfy those concerns or resolve the issue
with the release team before committing your change.  If after one
day, you have received no objections and someone has signed onto your
change, you may commit your change.  You may also commit your change
if no one objects within five days, even if no one has signed onto it.

When you check in your change, be sure to include a clear log message.
Explain why you are making the change you are making if it's not
obvious.

Reviewing changes
-----------------

Sometimes you can review a change by looking at the patch.  Other
times you will want to check out a tree and apply the patch, with
"patch -E -p < message-file" if you have the mail message in a file,
or "dsgrep -p -t trn-number source-reviewers | patch -E -p" if what
you have is a transaction number in the source-reviewers discuss
meeting.

When reviewing a change, be sure to make your position on the change
clear.  Say "I object to this change" if you are not merely voicing a
concern, or "I would like these questions answered before this change
is committed" if you have asked questions and are not merely curious.
When your objections are responded to, you should in turn respond in a
timely fashion saying whether your objections have been satisfied or
not.  If the dispute appears intractable, say so, so that the issue
may be brought up before the release team.

If you have reviewed a change carefully and have found nothing wrong
with it, and no one else has responded to the change, you should sign
onto the change rather than remaining silent.  You are encouraged to
try out changes before signing onto them, but in some cases the
inconvenience outweights the benefit of this consideration.

Early checkins
--------------

In some cases it may be appropriate to check in a change in advance of
the normal review period.  The following should be true of those
cases:

  1. The change is obvious and noncontroversial, such as a fix for a
     syntax error.

  2. The problem being fixed is causing an immediate difficulty,
     usually "I'm doing a build of /mit/source and it blows out at
     this point."

The change should still be sent to source-reviewers with a note about
the early checkin.  If the immediate difficulty is "the wash is broken
and I want the next wash to work," then it is good to get a positive
review of the change before checking it in.  Close to a release cycle,
though, that can be ignored.

Third-party sources
-------------------

"cvs import" is a fragile system with lots of flaws and corner cases.
Fortunately, we have a script to make imports convenient and mostly
error-free.  It lives in $CVSROOT/CVSROOT/import.sh, and is documented
briefly in comments at the top of the script.  Here are some use
cases:

  # Import a nicely named tarfile.
  $CVSROOT/CVSROOT/import.sh /tmp/bash-2.03.tar.gz

  # Import a not so nicely named tarfile.
  $CVSROOT/CVSROOT/import.sh -n pine -v 4.53 /tmp/pine4.53.tar.bz2

  # Import into a non-default repository directory.
  $CVSROOT/CVSROOT/import.sh -d third/glib2 /tmp/glib-2.2.1.tar.bz2

  # Import when old-version detection doesn't work right
  $CVSROOT/CVSROOT/import.sh -o 0.2.34 /tmp/esound-0.2.35.tar.bz2

After the initial import, here are some things to pay attention to
when adding or updating a piece of third-party software:

  * If the package's build system does not use autoconf, you will
    probably need to write a Makefile.athena file telling the build
    system how to build it.

  * If the package's build system does use autoconf, you may need to
    write a configure.athena giving special options to pass to the
    configure script.

  * A few packages will need to be taught how to use DESTDIR.  Make
    sure that DESTDIR references don't make it into the installed
    program.

  * If the package installs a file setuid, it needs to specify the
    owner (probably "-o root" if it didn't specify one before).
    Likewise, a setgid program needs a specified group owner, although
    this is usually done already.  Other than that, our fix_owners
    program will coerce unspecified owners and groups to 0.

  * The package should create directories before installing files in
    them.

  * If possible, test your package's build and install.  Preferrably,
    use the "do" command, something like:

      do dist
      do prepare
      do
      do -d /var/tmp/inst install

    (Replace "do" with "sh /mit/source/packs/build/do.sh" or use a
    shell alias.)  This testing may not be possible if the package
    depends on other packages not in the current Athena release.