@c -*- coding: utf-8; mode: texinfo; -*-

@include included/helpus.itexi

@node Introduction to contributing
@chapter Introduction to contributing

This chapter presents a quick overview of ways that people can
help LilyPond.

@menu
* Help us::
* Overview of work flow::
* Summary for experienced developers::
* Mentors::
@end menu


@node Help us
@section Help us

@helpusNeed

@helpusSimple

@helpusAdvanced


@node Overview of work flow
@section Overview of work flow

@advanced{Experienced developers should skip to
@ref{Summary for experienced developers}.}

Git is a @emph{version control system} that tracks the history of
a program's source code.  The LilyPond source code is maintained
as a Git repository, which contains:

@itemize
@item
all of the source files needed to build LilyPond, and

@item
a record of the entire history of every change made to every file
since the program was born.
@end itemize

The @q{official} LilyPond Git repository is hosted by the GNU
Savannah software forge at @uref{http://git.sv.gnu.org}.
Although, since Git uses a @emph{distributed} model, technically
there is no central repository.  Instead, each contributor keeps a
complete copy of the entire repository (about 116MB).

Changes made within one contributor's copy of the repository can
be shared with other contributors using @emph{patches}.  A patch
is a simple text file generated by the @command{git} program that
indicates what changes have been made (using a special format).
If a contributor's patch is approved for inclusion (usually
through the mailing list), someone on the current development team
will @emph{push} the patch to the official repository.

The Savannah software forge provides two separate interfaces for
viewing the LilyPond Git repository online: @emph{cgit} and
@emph{gitweb}.  The cgit interface should work faster than gitweb
in most situations, but only gitweb allows you to search through
the source code using @command{grep}, which you may find useful.
The cgit interface is at
@uref{http://git.sv.gnu.org/cgit/lilypond.git/} and the gitweb
interface is at
@uref{http://git.sv.gnu.org/gitweb/?p=lilypond.git}.

Git is a complex and powerful tool, but tends to be confusing at
first, particularly for users not familiar with the command line
and/or version control systems.  We have created the
@command{lily-git} graphical user interface to ease this
difficulty.

@emph{Compiling} (@q{building}) LilyPond allows developers to see
how changes to the source code affect the program itself.
Compiling is also needed to package the program for specific
operating systems or distributions.  LilyPond can be compiled from
a local Git repository (for developers), or from a downloaded
tarball (for packagers).  Compiling LilyPond is a rather involved
process, and most contributor tasks do not require it.

Contributors can contact the developers through the
@q{lilypond-devel} mailing list.  The mailing list archive is
located at
@uref{http://lists.gnu.org/archive/html/lilypond-devel/}.  If you
have a question for the developers, search the archives first to
see if the issue has already been discussed.  Otherwise, send an
email to @email{lilypond-devel@@gnu.org}.  You can subscribe to
the developers' mailing list here:
@uref{http://lists.gnu.org/mailman/listinfo/lilypond-devel}.

@warning{Contributors on Windows or MacOS X wishing to compile
code or documentation are strongly advised to use our Ubuntu
LilyPond Developer Remix, as discussed in @ref{Quick start}.}


@node Summary for experienced developers
@section Summary for experienced developers

If you are already familiar with typical open-source tools, here's
what you need to know:

@itemize
@item @strong{source repository}:
hosted by GNU savannah.

@example
@uref{http://git.savannah.gnu.org/gitweb/?p=lilypond.git}
@end example

@item @strong{mailing lists}:
given on @rweb{Contacts}.

@item @strong{branches}:

@itemize
@item @code{master}:
base your work from this, but do @strong{not push} to it.

@item @code{staging}:
after a successful review (see below), push here.

@item @code{lilypond/translation}:
translators should base their work from this, and also push to it.

@item @code{dev/foo}:
feel free to push any new branch name under @code{dev/}.

@end itemize

@item @strong{regression tests}:
also known as @qq{regtests}; this is a collection of more than a
thousand .ly files.  We track the output of those files between
versions.

If a patch introduces any unintentional changes to the regtests,
we will likely reject it -- make sure that you are aware and can
explain any regtest changes.  More info in @ref{Regression tests}.

@item @strong{reviews}:
after finishing work on a patch or branch:

@enumerate
@item
upload it with our custom @code{git-cl}.  In addition to uploading
it to the google rietveld code review tool, this adds a tracker
issue so that we don't lose your patch.  The @qq{status} of your
patch is kept on the issue tracker; see @ref{Issues}.

@example
@uref{https://github.com/gperciva/git-cl}
@end example

Your patch will be given @code{Patch-new} status.  More info in
@ref{Uploading a patch for review}.

@item
If your patch passes some automatic tests, it will be given
@code{Patch-review} status.  This generally happens within 24
hours.

@item
After that, the patch must wait for the next @qq{patch countdown},
which occur 3 times a week.  If there are a lot of patches waiting
for a countdown, a subset of patches are chosen randomly.  When
your patch is put on a countdown, it will be given
@code{Patch-countdown} status.

@item
The countdown is a 48-hour period which gives other developers one
last chance to review the patch.  If no significant problems are
found, your patch will be given @code{Patch-push} status.

@item
You may now either push it to the @code{staging} branch, or email
your patch (created with @w{@code{git format-patch}}) to somebody
who will push it for you.

@end enumerate

@advanced{Yes, this process means that most patches wait between
60-120 hours before reaching master.  This is unfortunate, but
given our limited resources for reviewing patches and a history of
unintended breakage in @code{master}, this is the best compromise
we have found.}

@c I don't think this is important enough to list here, but I may
@c change my mind and/or leave a link to a later CG section.
@ignore
@item @strong{code style}:
C++ code should be formatted with
@file{scripts/auxiliar/fixcc.py}, which requires
@url{http://astyle.sourceforge.net/, astyle 2.02}.  However, we
are not very strict about this requirement.

At the moment, scheme code should be formatted @qq{like emacs does
it}.  We are working on an automated tool to simplify this step.
However, we are not very strict about this requirement either.
@end ignore

@end itemize


@node Mentors
@section Mentors

We have a semi-formal system of mentorship, similar to the
medieval @qq{journeyman/master} training system.  New contributors
will have a dedicated mentor to help them @qq{learn the ropes}.

@warning{This is subject to the availability of mentors; certain
jobs have more potential mentors than others.}

@subheading Contributor responsibilities

@enumerate

@item
Ask your mentor which sections of the CG you should read.

@item
If you get stuck for longer than 10 minutes, ask your mentor.
They might not be able to help you with all problems, but we find
that new contributors often get stuck with something that could be
solved/explained with 2 or 3 sentences from a mentor.

@item
If you have been working on a task much longer than was originally
estimated, stop and ask your mentor.  There may have been a
miscommunication, or there may be some time-saving tips that could
vastly simply your task.

@item
Send patches to your mentor for initial comments.

@item
Inform your mentor if you're going to be away for a month, or if
you leave entirely.  Contributing to lilypond isn't for everybody;
just let your mentor know so that we can reassign that work to
somebody else.

@item
Inform your mentor if you're willing to do more work -- we always
have way more work than we have helpers available.  We try to
avoid overwhelming new contributors, so you'll be given less work
than we think you can handle.

@end enumerate


@subheading Mentor responsibilities

@enumerate

@item
Respond to questions from your contributor(s) promptly, even if
the response is just @qq{sorry, I don't know} or @qq{sorry, I'm
very busy for the next 3 days; I'll get back to you then}.  Make
sure they feel valued.

@item
Inform your contributor(s) about the expected turnaround for your
emails -- do you work on lilypond every day, or every weekend, or
what?  Also, if you'll be unavailable for longer than usual (say,
if you normally reply within 24 hours, but you'll be at a
conference for a week), let your contributors know.  Again, make
sure they feel valued, and that your silence (if they ask a
question during that period) isn't their fault.

@item
Inform your contributor(s) if they need to do anything unusual for
the builds, such as doing a @qq{make clean / doc-clean} or
switching git branches (not expected, but just in case...)

@item
You don't need to be able to completely approve patches.  Make
sure the patch meets whatever you know of the guidelines (for doc
style, code indentation, whatever), and then send it on to the
frog list or -devel for more comments.  If you feel confident
about the patch, you can push it directly (this is mainly intended
for docs and translations; code patches should almost always go to
-devel before being pushed).

@item
Keep track of patches from your contributor.  Either upload them
to Rietveld yourself, or help+encourage them to upload the patches
themselves.  When a patch is on Rietveld, it's your responbility
to get comments for it, and to add a link to the patch to the
google tracker.  (tag it @qq{patch-new}, or @qq{patch-review} if
you feel very confident in it)

@item
Encourage your contributor to review patches, particularly your
own!  It doesn't matter if they're not familiar with C++ / scheme
/ build system / doc stuff -- simply going through the process is
valuable.  Besides, anybody can find a typo!

@item
Contact your contributor at least once a week.  The goal is just
to get a conversation started -- there's nothing wrong with simply
copy&pasting this into an email:

@example
Hey there,

How are things going?  If you sent a patch and got a review, do
you know what you need to fix?  If you sent a patch but have no
reviews yet, do you know when you will get reviews?  If you are
working on a patch, what step(s) are you working on?
@end example


@end enumerate