source: trunk/doc/procedures @ 12753

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
        Updating 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 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 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.

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. Use "cvs diff -c -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.)

        4. 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 

        5. Send your diffs, along with a clear description of the
           change you are making, to source-reviewers@mit.edu.

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 full working 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.

Updating third-party sources
----------------------------

For modules in the third hierarchy, we generally use the "cvs import"
command to track development from outside.  (To find out if this
applies to a given module, to a "cvs log" of a file in the tree; if
you see a revision 1.1.1.1, then we're using cvs import.)  Do not
check in a new outside version of a third-party package onto the
mainline if it was originally imported with cvs import; it's very
difficult to recover from that particular mistake.  Do, however, check
local changes you made yourself onto the mainline.  Always refer to
doc/third-party before doing an import to see if there are any special
notes on the module you are importing.

Generally, you should only import "clean" third-party source trees
with no modifications.  If you absolutely need to make changes to the
source tree before importing it (check with a release engineer before
deciding that you have to), make a note in the doc/third-party file so
that people doing future imports will know about it.

If you add a new piece of third-party software or import a new
version, you should look over doc/third-party and see if any notes
should be added or modified.  This file is instrumental in locating
new versions of software.