Update contributor documentation

Summary:
It's fairly common for people to show up and be interested in finding easy stuff to work on. This stuff basically doesn't exist and probably never will: it doesn't make much sense to deliberately leave easy bugs broken just because someone might show up and want to fix a couple of easy bugs.

Almost all of the work that's valuable to us requires a depth or bredth of context which can't be acquired in a few hours here and there, and probably always will. I think it also always //should//, in that as long as we continue refactoring and clearing technical debt aggressively and having solid static analysis support tools, we should never have a large backlog of human-intelligence codebase tasks. The closest we've ever come were probably `pht()` and `phutil_tag()`, which both have a lot of subtleties and we mostly automated `phutil_tag()` anyway. These tasks are also //incredibly boring// to write and review.

So, accept this as a reality and realign the contributor documentation to try to deal with this case:

  - Set expectations about starter tasks not existing and throwing a couple of hours at the project writing code being a hard path.
  - Suggest non-code contributions which anyone can do.
  - Segue into code contributions with context and suggestions.

Test Plan: Generated and read documentation.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D8872

src/docs/contributor/contrib_intro.diviner

@@ -3,43 +3,110 @@
 
 Introduction to contributing to Phabricator, Arcanist and libphutil.
 
-= You Are Awesome =
+Overview
+========
 
-Contributors are awesome. If you're thinking about contributing, that means
-you're thinking about being awesome. That already makes you a little bit
-awesome. But if you contribute you'll definitely be really, seriously awesome.
+If you'd like to contribute to Phabricator, this document can guide you though
+ways you can help improve the project.
+
+Writing code is valuable, but often isn't the best or easiest way to contribute.
+In most cases we are pretty good at fixing easy stuff quickly, so we don't have
+a big pile of easy stuff sitting around waiting for new contributors.
+
+This can make it difficult to contribute code if you only have a little bit of
+time to spend since most of the work that needs to be done usually requires some
+heavy lifting.
+
+Without writing any code, learning the whole codebase, making a big time
+commitment, or having to touch PHP, here are some ways you can materially
+contribute to Phabricator:
+
+  - Send us an email or drop by IRC just to say "thanks". A big part of the
+    reason we build this software is to help people solve problems, and knowing
+    that our efforts are appreciated is really rewarding. You can find ways to
+    get in touch in @{article:Give Feedback! Get Support!}
+  - Recommend Phabricator to people who you think might find it useful. Our
+    most powerful growth channel is word of mouth, and mentioning or tweeting
+    about Phabricator helps the project grow. If writing a tweet sounds like
+    too much work, you can use one of these form tweets written by our PR
+    department to quickly and easily shill on our behalf. Hail corporate!
+
+> Phabricator seems like it's pretty okay
+
+> I am not being paid to mention Phabricator in this extemporaneous, completely organic tweet
+
+> Phabricator is objectively the best thing. Source: I am a certified, internationally recognized expert.
+
+  - Report bugs and request features. We may not always be able to fix or build
+    things right away, but knowing about issues users are encountering or
+    features they'd like to see improves our ability to plan and prioritize.
+    For ways to do this, see @{article:Give Feedback! Get Support!}
+  - Give us feedback on planned features. Most of what we'll build in the next
+    6-12 months currently exists on the [[ Roadmap ]] or in Maniphest. Telling
+    us about use cases you have can help us build better products when the time
+    comes to write the code.
+  - Hang out in IRC, and maybe answer a question or two. IRC is a completely
+    legit place for serious hackers to hang out anyway, but while you're there
+    you might see someone ask a question that you know the answer to. Helping
+    them out (or pointing them to the right documentation) is a big help to us.
+    You can find details about the IRC channel in
+    @{article:Give Feedback! Get Support!}
+
+If all of this sounds nice but you really just want to write some code, that's
+awesome too. The rest of this document (and the other articles in this section
+of the documentation) can help you get started.
 
 = Legal Stuff =
 
-Before we can accept contributions, you need to submit a super fine and fancy
-legal document called a Facebook Contributor License Agreement, which you can
-find here:
+Before we can accept source code contributions, you need to submit a super fine
+and fancy legal document called a Facebook Contributor License Agreement, which
+you can find here:
 
 https://developers.facebook.com/opensource/cla
 
 = Not Sure Where To Get Started? =
 
-If you want to contribute but aren't sure how (or want to try submitting a small
-patch before you build something bigger) you can search the Phabricator
-development install for open tasks (these are pretty up-to-date) or come find
-us in IRC and ask for some pointers.
+Because we're usually quick to fix easy bugs and issues, we often don't have a
+very good backlog of starter tasks.
+
+You can try searching in Maniphest for tasks tagged with "Easy", which might
+have something, but a lot of time this list is small and the tasks on it aren't
+very fun or interesting even if they aren't technically too difficult.
+
+In general, the best way to contribute is to come to us with a problem you
+encountered or something you're interested in building, and then work with us
+to find a solution to it or a plan to build it. We can help turn a hacky patch
+into something that's upstreamable, and you'll get a fix or feature you want.
+
+You can also look though the rest of the open tasks for something more
+substantive that you're interested in. This will give you a better chance of
+finding something that's relevant to you, but many tasks are large or blocked
+by other large tasks.
+
+If you do find something, feel free to leave a comment like "I'm interested in
+working on this, is this something I could reasonably help with?". We're happy
+to walk through things, break larger tasks down into more detail, provide
+pointers to similar changes and the right places in the codebase to get started,
+and generally figure out how to attack a problem.
+
+You can also just come find us in IRC and ask how to get started.
 
 = Submitting Patches =
 
 To submit patches against libphutil, Arcanist or Phabricator, create a commit
-and use ##arc## to send it for review (probably with ##epriestley## as a
-reviewer):
+and use `arc` to send it for review (probably with `epriestley` as a reviewer):
 
   $ arc diff
 
-When your change is accepted, send a pull request on GitHub. (You can also
-just submit a pull request, but Differential is preferred for nontrivial
-changes.)
+You can also submit a pull request on GitHub, but Differential is strongly
+preferred.
 
 = Suggested Reading =
 
 You should read the relevant coding convention documents before you submit a
-change and make sure you're following the project guidelines:
+change. If you're a new contributor, you don't need to worry about this too
+much. Just try to make your code look similar to the code around it, and we
+can help you through the details during review.
 
   - @{article:General Coding Standards} (for all languages)
   - @{article:PHP Coding Standards} (for PHP)