Migrate Differential comments to ApplicationTransactions

Summary:
Ref T2222. This is the big one.

This migrates each `DifferentialComment` to one or more ApplicationTransactions (action, cc, reviewers, update, comment, inlines), and makes `DifferentialComment` a double-reader for ApplicationTransactions.

The migration is pretty straightforward:

  - If a comment took an action not otherwise covered, it gets an "action" transaction. This is something like "epriestley abandoned this revision.".
  - If a comment updated the diff, it gets an "updated diff" transaction. Very old transactions of this type may not have a diff ID (probably only at Facebook).
  - If a comment added or removed reviewers, it gets a "changed reviewers" transaction.
  - If a comment added CCs, it gets a "subscribers" transaction.
  - If a comment added comment text, it gets a "comment" transaction.
  - For each inline attached to a comment, we generate an "inline" transaction.

Most comments generate a small number of transactions, but a few generate a significant number.

At HEAD, the code is basically already doing this, so comments in the last day or two already obey these rules, roughly, and will all generate only one transaction (except inlines).

Because we've already preallocated PHIDs in the comment text table, we only need to write to the transaction table.

NOTE: This significantly degrades Differential, making inline comments pretty much useless (they each get their own transaction, and don't show line numbers or files). The data is all fine, but the UI is garbage now. This needs to be fixed before we can deploy this to users, but it's easily separable since it's all just display code.

Specifically, they look like this:

{F112270}

Test Plan:
I've migrated locally and put things through their paces, but it's hard to catch sketchy stuff locally because most of my test data is nonsense and bad migrations wouldn't necessarily look out of place.
IMPORTANT: I'm planning to push this to a branch and then shift production over to the branch, and run it for a day or two before bringing it to master.

I generally feel good about this change: it's not that big since we were able to separate a lot of pieces out of it, and it's pretty straightforward. That said, it's still one of the most scary/dangerous changes we've ever made.

Reviewers: btrahan

CC: chad, aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8210
Always provide a valid content source for DifferentialCommentEditor

Summary: Ref T2222. On the `tmp.differential` branch, we're currently having
issues parsing commits which reference Differential revisions, because the
"user closed this revision (closed by commit xyz)" message is fataling:

  [2014-02-13 14:12:36] EXCEPTION: (PhutilProxyException) Error while
  executing task ID 345358 from queue. {>} (AphrontQueryException)
  #1048: Column 'contentSource' cannot be null

Specifically, the MessageParser pathway for CommentEditor doesn't set a content
source. Make sure CommentEditor always sets a content source.

(This is also causing a buildup of diffs on D8212 and D8211.)

Auditors: btrahan
Use timeline view in Differential and make inlines somewhat usable again

Summary:
Ref T2222. This gets rid of Differential's custom view and uses a standard view instead.

This also mostly fixes the rendering logic for inlines.

This is headed to the `tmp.differential` branch.

Test Plan: {F112696}

Reviewers: btrahan

Reviewed By: btrahan

CC: chad, aran

Maniphest Tasks: T1790, T2222

Differential Revision: https://secure.phabricator.com/D8215
Fix double-rendering of inline comments in mail

Summary: Ref T2222. This is a `tmp.differential`-only issue. Inline comment transactions now have content, so we treat them like body text. We also render them separately as inline text. This produces mail where inlines are rendered twice.

Test Plan: Sent myself mail, saw only one copy of inlines.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8216
Make Asana bridge work with new Differential transactions

Summary: Ref T2222. Unbreak the Asana/JIRA bridge.

Test Plan: {F112712}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8217
Add some missing text for Differential inline transactions

Summary: Ref T2222. Add inline and default text.

Test Plan: Feed works again.

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8218
Fix two issues with Differential Transactions

Summary: With symbols, the transactions fataled on `getID()`. Also my line
number sorting was a bit goofy.

Auditors: btrahan
Fix transaction comment bug

Summary: form.reset() resets a form to whatever values were present when the form was loaded into the DOM. Instead, grab all the pertinent form bits and set there values to "clear". I don't think there's too much utility in putting this somewhere more general, but it could be something like DOM.clearForm(form) or something. Fixes T3629.

Test Plan:
repro'd original issue

 - open legalpad doc (or your favorite application transaction powered app)
 - type in a comment but do not submit (you are creating a draft) e.g. "foo"
 - reload page and note comment appears e.g. "foo"
 - change comment e.g. "foobar"
 - submit comment
 - BUG - after submission, the comment reverts to the comment at initial page load e.g. "foo"

then after this patch, I can't repro it anymore with these steps - the comment is correctly blank

 NOTE: this will need to be tested with more complicated forms.

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T3629

Differential Revision: https://secure.phabricator.com/D8220
Pass $all_changesets, not $changesets, to inline rendering logic

Summary: `$all_changesets` has all the changesets.

Auditors: btrahan
Use pixel as background of timeline

Summary: Makes the line in timeline a background "image" instead.

Test Plan: Tested Desktop, Mobile, and Tablet breakpoints with lots of content.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8221
Don't show "edit" links in Differential for now

Summary: Ref T2222. These don't work yet. We just have to copy a couple fields, but let's sort that out later since this is purely a new feature.

Test Plan: Looked at a revision, no edit links.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8222
Provide transaction strings, icons and colors for Differential

Summary: Ref T2222. Once these are live, yell if any of them seem off. I tried to mostly stay consistent-ish with what we had before.

Test Plan: Looked at a bunch of revisions and saw more detailed, colorful transactions.

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8223
Fix inline comment links for non-visible comments

Summary: Ref T2222. Restore this funky is-visible / inline-is-elsewhere logic.

Test Plan: Updated a revision, saw all the inlines render properly when looking at various diffs and versus-diffs. Clicked inline links.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8224
Merge Differential comment migration to ApplicationTransactions

Summary: Ref T2222. This merges the `tmp.differential` branch, including the
comment -> application transaction migration, to `master`.

Auditors: btrahan
Automatically inline small images using data URIs

Summary: Fixes T3300. Images under 32KB are inlined automatically into CSS using data URIs; larger images remain as normal links. I picked the 32KB threshold arbitrarily, based on it looking roughly like it got reasonable results on `core.pkg.css` (inlining most of the random stuff, but not inlining all the 2X sprites and such).

Test Plan: Loaded site, browsed around, looked at generated CSS.

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T3300

Differential Revision: https://secure.phabricator.com/D8225
Link the "(board)" text after project references in Maniphest

Summary: Fixes T4429. Shows and allows you to click through on board links when a task appears on workboards.

Test Plan:
{F112837}

Clicked the links.

Reviewers: chad, btrahan

Reviewed By: chad

CC: chad, aran

Maniphest Tasks: T4429

Differential Revision: https://secure.phabricator.com/D8226
Show detailed ApplicationTransaction changes in a dialog

Summary: Fixes T4423. This works better and is simpler and more flexible.

Test Plan: Clicked "(Show Details)", got a popup with the details.

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Maniphest Tasks: T4423

Differential Revision: https://secure.phabricator.com/D8227
Remove spacing after timeline on diffs

Summary: I assume this box is always after timeline

Test Plan: test a diff or two

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8230
Hide seen transactions by default in all modern applications

Summary:
Ref T2222. This restores the "N older comments are hidden." shield to all ApplicationTransactions applications. Roughly the rule this uses is that transactions older than your most recent comment are hidden, under the assumption that you've already read and dealt with them, since you replied afterward. Then we show your last comment to remind/contextualize you, and anything afterward. We also don't hide transactions if we'd only be hiding a handfull, and we never hide the few most recent transactions.

This might need some #design help.

Test Plan:
The tricky part here is the anchor rule, which deals with the case where you follow a link to `T123#4`, but that would normally be hidden. We simulate a click on "show all" if you hit an anchor which is hidden. Here's what it looks like in Maniphest:

{F112891}

Reviewers: btrahan, chad

Reviewed By: btrahan

CC: chad, aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8229
Begin modularizing typeahead sources

Summary:
Ref T4420. This sets up the basics for modular typeahead sources. Basically, the huge `switch()` is just replaced with class-based runtime dispatch.

The only clever bit I'm doing here is with `CompositeDatasource`, which pretty much just combines the results from several other datasources. We can use this to implement some of the weird cases where we need multiple types of results, although I think I can entirely eliminate many of them entirely. It also makes top-level implementation simpler, since more logic can go inside the sources.

Sources are also application-aware, will be responsible for placeholder text, and have a slightly nicer debug view.

Test Plan: {F112859}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4420

Differential Revision: https://secure.phabricator.com/D8228