(emacs)Sending Patches

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Sending Patches for GNU Emacs

   If you would like to write bug fixes or improvements for GNU Emacs,
that is very helpful.  When you send your changes, please follow these
guidelines to make it easy for the maintainers to use them.

   If you don't follow these guidelines, your information might still be
useful, but using it will take extra work.  Maintaining GNU Emacs is a
lot of work in the best of circumstances, and we can't keep up unless
you do your best to help.

   * Send an explanation with your changes of what problem they fix or
     what improvement they bring about.  For a bug fix, just include a
     copy of the bug report, and explain why the change fixes the bug.

     (Referring to a bug report is not as good as including it, because
     then we will have to look it up, and we have probably already
     deleted it if we've already fixed the bug.)

   * Always include a proper bug report for the problem you think you
     have fixed.  We need to convince ourselves that the change is
     right before installing it.  Even if it is correct, we might have
     trouble understanding it if we don't have a way to reproduce the

   * Include all the comments that are appropriate to help people
     reading the source in the future understand why this change was

   * Don't mix together changes made for different reasons.  Send them

     If you make two changes for separate reasons, then we might not
     want to install them both.  We might want to install just one.  If
     you send them all jumbled together in a single set of diffs, we
     have to do extra work to disentangle them--to figure out which
     parts of the change serve which purpose.  If we don't have time
     for this, we might have to ignore your changes entirely.

     If you send each change as soon as you have written it, with its
     own explanation, then the two changes never get tangled up, and we
     can consider each one properly without any extra work to
     disentangle them.

   * Send each change as soon as that change is finished.  Sometimes
     people think they are helping us by accumulating many changes to
     send them all together.  As explained above, this is absolutely
     the worst thing you could do.

     Since you should send each change separately, you might as well
     send it right away.  That gives us the option of installing it
     immediately if it is important.

   * Use `diff -c' to make your diffs.  Diffs without context are hard
     to install reliably.  More than that, they are hard to study; we
     must always study a patch to decide whether we want to install it.
     Unidiff format is better than contextless diffs, but not as easy
     to read as `-c' format.

     If you have GNU diff, use `diff -cp', which shows the name of the
     function that each change occurs in.

   * Write the change log entries for your changes.  This is both to
     save us the extra work of writing them, and to help explain your
     changes so we can understand them.

     The purpose of the change log is to show people where to find what
     was changed.  So you need to be specific about what functions you
     changed; in large functions, it's often helpful to indicate where
     within the function the change was.

     On the other hand, once you have shown people where to find the
     change, you need not explain its purpose. Thus, if you add a new
     function, all you need to say about it is that it is new.  If you
     feel that the purpose needs explaining, it probably does--but the
     explanation will be much more useful if you put it in comments in
     the code.

     Please read the `ChangeLog' file to see what sorts of information
     to put in, and to learn the style that we use.  If you would like
     your name to appear in the header line showing who made the
     change, send us the header line.

   * When you write the fix, keep in mind that we can't install a
     change that would break other systems.  Please think about what
     effect your change will have if compiled on another type of system.

     Sometimes people send fixes that *might* be an improvement in
     general--but it is hard to be sure of this.  It's hard to install
     such changes because we have to study them very carefully.  Of
     course, a good explanation of the reasoning by which you concluded
     the change was correct can help convince us.

     The safest changes are changes to the configuration files for a
     particular machine.  These are safe because they can't create new
     bugs on other machines.

     Please help us keep up with the workload by designing the patch in
     a form that is clearly safe to install.

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