Fix two bugs with Config's Edit controller.

Summary:
* When we restored to the default value, we did, in fact delete the row from the
  database, but then a few lines later down, we saved it again. This patch causes
  the controller to return early on delete, like it was supposed to do to begin
  with.
* When checking the user's input value for `null` (since PHP's JSON encoder will
  return `null` on failure), check the value that the user gave, not the value
  that we default to (which is often `null` anyway). Oops.

Test Plan:
* Saved an empty text field and saw the delete work properly and NOT get
  re-added.
* Put `null` in the text field, and saved successfully.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4300
Add a local configuration source and a non-environmental ENV config source

Summary:
See discussion in T2221. Before we can move configuration to the database, we have a bootstrapping problem: we need database credentials to live //somewhere// if we can't guess them (and we can only really guess localhost / root / no password).

Some options for this are:

  - Have them live in ENV variables.
    - These are often somewhat unfamiliar to users.
    - Scripts would become a huge pain -- you'd have to dump a bunch of stuff into ENV.
    - Some environments have limited ability to set ENV vars.
    - SSH is also a pain.
  - Have them live in a normal config file.
    - This probably isn't really too awful, but:
    - Since we deploy/upgrade with git, we can't currently let them edit a file which already exists, or their working copy will become dirty.
    - So they have to copy or create a file, then edit it.
    - The biggest issue I have with this is that it will be difficult to give specific, easily-followed directions from Setup. The instructions need to be like "Copy template.conf.php to real.conf.php, then edit these keys: x, y, z". This isn't as easy to follow as "run script Y".
  - Have them live in an abnormal config file with script access (this diff).
    - I think this is a little better than a normal config file, because we can tell users 'run phabricator/bin/config set mysql.user phabricator' and such, which is easier to follow than editing a config file.

I think this is only a marginal improvement over a normal config file and am open to arguments against this approach, but I think it will be a little easier for users to deal with than a normal config file. In most cases they should only need to store three values in this file -- db user/host/pass -- since once we have those we can bootstrap everything else. Normal config files also aren't going away for more advanced users, we're just offering a simple alternative for most users.

This also adds an ENVIRONMENT file as an alternative to PHABRICATOR_ENV. This is just a simple way to specify the environment if you don't have convenient access to env vars.

Test Plan: Ran `config set x y`, verified writes. Wrote to ENVIRONMENT, ran `PHABRICATOR_ENV= ./bin/repository`.

Reviewers: btrahan, vrana, codeblock

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2221

Differential Revision: https://secure.phabricator.com/D4294
Detect and raise setup warnings from within Phabricator

Summary:
This is basicaly a light version of D4286. The major problem with D4286 is that it's a huge leap and completely replaces the setup process in one step.

Instead, I want to do this:

  - Add the post-setup warnings (yellow bar with "6 unresolved warnings...").
  - Copy all setup checks into post-setup warnings (so every check has an old-style check and a new-style check).
  - Run that for a little bit and make sure it's stable.
  - Implement fatal post-setup checks (the red screen, vs the yellow bar).
  - Run that for a little bit.
  - Nuke setup mode and delete all the old checks.

This should give us a bunch of very gradual steps toward the brave new world of simpler setup.

Test Plan:
 - Faked APC setup failures, saw warnings raise.
 - Verified that this runs after restart (get + set).
 - Verified that this costs us only one cache hit after first-run (get only).

Reviewers: btrahan, codeblock, vrana, chad

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2228

Differential Revision: https://secure.phabricator.com/D4295
Move all CSS "z-index" rules to "z-index.css", fix Differential z-index problem

Summary: We have enough z-index rules that they're fairly hard to visualize with "git grep". Consolidate them. Then fix T2253 (missing z-index on left menu background).

Test Plan: Made a Differential window really narrow, then scrolled it horizontally.

Reviewers: btrahan, chad, ender

Reviewed By: chad

CC: aran

Maniphest Tasks: T2253

Differential Revision: https://secure.phabricator.com/D4302
Minor, fix a missing z-index.
Improve S3 integration

Summary:
  - Fixes T2257. We wrote a 0-length file (erroneously?) and currently throw when retrieving it. This also happens if you intentionally upload an empty file. I'm not sure what happened with the image: we check for errors during the write, so its existence implies S3 told us the write was successful and then lost the data. Since this is a one-off, I'm not too worried about it. The indistinguishable case of an actually empty file is fixed, at least.
  - Writes to a directory like "phabricator/ab/cd/efgh" instead of "phabricator/abcdefgh". When I had to go look for the file on S3 it took a few minutes of scrolling since the web interface isn't very fast. Make it so a file can be located by navigating through pieces of the hash.

Test Plan: Viewed an empty file, no fatal. Viewed the file from T2257 locally, no fatal (no data either, but it's gone). Uploaded a file, saw a nice path.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2257

Differential Revision: https://secure.phabricator.com/D4303
Fix write to undefined property $_hunks

Summary: Some time long in the past, this was renamed to unsavedHunks. Fixes T2249.

Test Plan: Ran `destroy_revision.php D20`, got a successful destruction.

Reviewers: btrahan, vrana

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2249

Differential Revision: https://secure.phabricator.com/D4304
Remove advice to "yum install php5-x" for RedHat

Summary: See D4295.

Test Plan: Cursory glance.

Reviewers: codeblock

Reviewed By: codeblock

CC: aran

Differential Revision: https://secure.phabricator.com/D4307
Begin moving Phabricator configuration into PHP

Summary: Ref T2255. Ref T2221. Lay the groundwork to move configuration into PHP, so we can show descriptions in the web UI, do typechecking, disable application options when an application is uninstalled, etc.

Test Plan:
{F28421}
{F28420}
{F28422}

Reviewers: codeblock, btrahan, vrana

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2221, T2255

Differential Revision: https://secure.phabricator.com/D4306
Improve resolution process for nonfatal setup issues

Summary:
  - When a setup issue is nonfatal (i.e., a warning), instruct the user to edit the value from the web UI instead of using `bin/config`.
  - When the user edits configuration in response to a setup issue, send them back to the issue when they're done.
  - When an issue relates to PHP configuration, link to the PHP documentation on configuration.
  - Add new-style setup check for timezone issues.

Test Plan: Mucked with my timezone config, resolved the issues I created.

Reviewers: codeblock, btrahan, vrana

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2221, T2228

Differential Revision: https://secure.phabricator.com/D4298
Remove "preview.viewport-meta-tag" config

Summary: This is obsolete with the 'device' => true stuff, which is more granular and generally better.

Test Plan: grep

Reviewers: btrahan, codeblock

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4309
Add "Developer" and "Access Log" config option groups, some types

Summary:
  - Add a "developer" option group.
  - Add an "access log" option group.
  - Render the types "bool", "int" and "string" in a more tailored way.
  - Add a config check for dead config. Right now this serves as a "TODO" list of things that need to be migrated.

Test Plan: Looked at config options, setup issues. Edited bool, int, string options.

Reviewers: codeblock, btrahan

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4308
Add Disqus, Facebook, Google, GitHub auth config; AWS config

Summary: Also improve behavior for the "unknown config" warning.

Test Plan: Looked at configs, went through unknown config workflow.

Reviewers: btrahan, codeblock

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4310
Display examples when editing configuratoin

Summary: Show example config values to the user when available.

Test Plan:
{F28465}
{F28466}

Reviewers: btrahan, codeblock

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2221, T2255

Differential Revision: https://secure.phabricator.com/D4311
Show all configuration defaults when editing configuration

Summary: Show the value for all loaded configuration sources.

Test Plan:
{F28469}

{F28470}

{F28471}

Reviewers: btrahan, codeblock

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4312
Show current value in configuration list; show default vs non-default values

Summary:
  - When viewing a config list, show the current effective value.
  - Add an icon showing default vs nondefault values.

Test Plan: {F28475}

Reviewers: btrahan, codeblock

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4313
Use transactions to show edit history for Configuration

Summary: Use ApplicationTransactions in Config to create an edit history. Resolves T2256.

Test Plan: {F28477}

Reviewers: btrahan, codeblock

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2256

Differential Revision: https://secure.phabricator.com/D4314
Allow configuration to be explicitly validated, including validation of complex attributes

Summary:
  - Allows us to implement setup warnings for edits which don't go through the web UI, e.g. "you edited a config file and set value X to something goofy".
  - Allows us to implement more sophisticated validations, beyond basic type checks (e.g., "phabricator.base-uri" must be a URI).
  - Fixes T358 (or, close enough -- fixes it for all options which have been migrated as per T2255.

Test Plan: Set "darkconsole.enabled" to "xyz" in my config, observed setup warning. Added fake validation, observed web UI edit error.

Reviewers: codeblock, btrahan

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255, T358

Differential Revision: https://secure.phabricator.com/D4315
Add "Core" config, with complex validation

Summary: This is more or less a copy of the validation which lives in `webroot/index.php` right now, but I don't want to wipe that out just yet because there's no way for normal users to see this new validation.

Test Plan: Tried to set "phabricator.base-uri" to crazy nonsense, was harshly rebuffed.

Reviewers: codeblock, btrahan

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4316
Add some more options to the "core" group.

Summary:
Refs #2255 and completes the first group ("CORE") in @epriestley's comment
thereof.

Test Plan: Saw the new options appear in the list and save correctly.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4317