Don't interpret `arc browse .` as a commit

Summary: Ref T5781. `git show .` works like HEAD, but that isn't what `arc browse .` means.

Test Plan: Ran `arc browse .` with a repository at a published commit.

Reviewers: chad, btrahan, avive, avivey

Reviewed By: avivey

Subscribers: epriestley, avivey

Maniphest Tasks: T5781

Differential Revision: https://secure.phabricator.com/D10197
Remove --background flag to prevent `arc` from hanging

Summary:
Ref T4281. A long time ago, we added a `--background` flag to let `arc lint` and `arc unit` run while you're typing a commit message, in some situations.

This code is only moderately beneficial and is way too complicated. Particularly, it has a long history of causing hangs (T4281, T2463), doesn't work on Windows, and is impossible to debug.

It's also running into a serious PHP bug with EAGAIN/EPIPE being indistinguishable that I haven't been able to find a reasonable workaround for in ~3-4 hours of trying.

All the pathways forward that I can see make this already-complex system more complex.

The major reason that this stuff is so complex is that the subprocess may need to prompt the user (notably, to apply patches from lint).

Instead, I'm going to simplify how `arc diff` interacts with `arc lint` and `arc unit`, so we can just fire-and-forget a background process, let it do as much work as it can without needing user input, and then pick up wherever it left off. This will be slightly less cool/magical, but it won't hang bizarrely and I will be able to debug it.

For now, simply remove the `--background` flag and behavior so `arc` works for everyone.

Test Plan: Ran `arc diff` to create this diff.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4281

Differential Revision: https://secure.phabricator.com/D10198
Make arcanist lint tests flexible about testcase formatting

Summary:
We currently require an exact number of "~" characters, but this is needless and error-prone.

Instead, allow any number larger than 3.

Test Plan:
  - Added meta test-case.
  - Ran `arc unit --everything`.

Reviewers: btrahan, thoughtpolice

Reviewed By: thoughtpolice

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D10251
[lint] Add HLint-based Haskell linter

Summary:
This adds a lint engine for `hlint`, which is the standard and most general Haskell lint tool around these days.

Signed-off-by: Austin Seipp <aseipp@pobox.com>

Test Plan: Install `hlint`, and run `arc unit`.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Projects: #arcanist

Differential Revision: https://secure.phabricator.com/D10250
Don't parse separator tabs as part of the filename in Git diffs which affect files with spaces

Summary:
Fixes T5870. When a filename contains spaces, Git will add a "\t" at the end of the "---" and "+++" lines. We currently consume this and think we're reading a file called "blah blah\t".

Instead, parse it out as not part of the filename.

Test Plan: Added failing unit test and made it pass.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5870

Differential Revision: https://secure.phabricator.com/D10267
Schedule repository updates from `arc commit`, not just `arc land`

Summary: Ref T5926. We only pass Phabricator an update hint from `arc land`, not from `arc commit`.

Test Plan:
  - Ran `arc land` and `arc commit` with `--trace`, saw hints go over the wire.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5926

Differential Revision: https://secure.phabricator.com/D10324
Arcanist - potentially fix some Windows badness

Summary: Fixes T5914, maybs.

Test Plan: will ask users in T5914

Reviewers: chad, epriestley

Reviewed By: chad, epriestley

Subscribers: chad, bluehawk, epriestley, Korvin

Maniphest Tasks: T5914

Differential Revision: https://secure.phabricator.com/D10333
Merge remote-tracking branch 'upstream/master'