Fail lint tests if no tests are found in the test directory

Summary: Ref T4570. Testing a directory with no recognized tests currently passes, but should fail.

Test Plan:
  - Ran `arc unit`.
  - Removed tests from a test directory, ran `arc unit`, got test failure.

Reviewers: leebyron, btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4570

Differential Revision: https://secure.phabricator.com/D8434
Fail Arcanist tests when they make zero assertions

Summary:
Fixes T4570. When a test case doesn't make any assertions, fail it:

  - A tiny fraction of tests pass by not throwing. These tests can easily make a trivial assertion. It took about 5 minutes to fix them all (D8435, D8436).
  - In other cases, no assertions means a test construction problem, as with T4570. In these cases, failing loudly catches a severe error.
  - Fixes the no-assertion test cases in `arcanist/`
  - Makes the PHP 5.4 test pass for the moment, see discussion in T4334.

Test Plan: Ran `arc unit --everything`.

Reviewers: leebyron, btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4570

Differential Revision: https://secure.phabricator.com/D8437
Fix unit test coverage for `NoseTestEngine`.

Summary:
I noticed that code coverage wasn't showing in Differential for
some repositories that we are using with Phabricator.

`arc unit` would should unit test coverage, but the paths were messy
(for example, `.//foo/bar.py` instead of `foo/bar.py`). As a result,
the code coverage info wasn't recognised as being for the correct
module.

I'm not sure why this logic is the way that it is... perhaps this is to
do with an older version of `nose` (I am using v1.3.0).

Test Plan:
I created a diff for an internal repository that we have, and
observed that code coverage was displayed in Differential.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran, seporaitis, avive, dctrwatson, zeeg

Differential Revision: https://secure.phabricator.com/D8433
Added some additional assertion methods.

Summary:
There are quite a few tests in Arcanist, libphutil and Phabricator that do something similar to `$this->assertEqual(false, ...)` or `$this->assertEqual(true, ...)`.

This is unnecessarily verbose and it would be cleaner if we had `assertFalse` and `assertTrue` methods.

Test Plan: I contemplated adding a unit test for the `getCallerInfo` method but wasn't sure if it was required / where it should live.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8460
Utilize `assertFalse` and `assertTrue` methods.

Summary:
Ref D8460.

Use `$this->assertFalse(...)` and `$this->assertTrue(...)` instead of `$this->assertEqual(false, ...)` and `$this->assertEqual(true, ...)` respectively.

Test Plan: `arc unit`

Reviewers: #blessed_reviewers, epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8461
Make assertTrue() / assertFalse() messages more descriptive

Summary: See discussion in D8460. Primarily, this prints out the failing value when a true/false assertion fails, so if it was something useful (like a function result) it's visible.

Test Plan:
Added `assertTrue("quack")`:

     FAIL  ArcanistDiffParserTestCase::testParser
  Assertion failed, expected 'true' (at ArcanistDiffParserTestCase.php:16).

  ACTUAL VALUE
  quack

Added `assertFalse("quack")`:

     FAIL  ArcanistDiffParserTestCase::testParser
  Assertion failed, expected 'false' (at ArcanistDiffParserTestCase.php:16).

  ACTUAL VALUE
  quack

Added `assertEqual("quack", "moo")`:

     FAIL  ArcanistDiffParserTestCase::testParser
  Assertion failed, expected values to be equal (at ArcanistDiffParserTestCase.php:16).
  Expected: quack
    Actual: moo

Reviewers: joshuaspence

Reviewed By: joshuaspence

CC: aran

Differential Revision: https://secure.phabricator.com/D8465
Ignore detached git branches.

Summary:
Fixes T4559.

It looks like the code currently (at least partially) handles this by checking for `(no branch)`. I suspect that the behaviour of `git` has changed (I am running version 1.9.0) because I haven't figured out what state to be in to cause `git` to output `(no branch)`.

Test Plan: Ran `arc branch` when on a detached branch.

Reviewers: #blessed_reviewers, epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T4559

Differential Revision: https://secure.phabricator.com/D8466
Add a linter for Dart files
Add lint engine for Taco projects
Add test engine for Dart

@astashov, `git pull` your arcanist repo and run `arc liberate`.
Only run Dart unit tests if a Dart file has changed
Fix issues with parsing Dart unit test output