Initial commit

Lint clean, has boilerplate and license information, and has diff
creation code from HHAST

.LICENSE_HEADER.hh.txt

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+/*
+ *  Copyright (c) 2017-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the MIT license found in the
+ *  LICENSE file in the root directory of this source tree.
+ *
+ */

.gitignore

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+vendor/
+*.swp
+*.swo
+.DS_Store

.hhconfig

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+assume_php=false

.travis.sh

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+#!/bin/sh
+set -ex
+hhvm --version
+
+composer install --ignore-platform-reqs
+
+hh_client
+
+#hhvm vendor/bin/phpunit
+hhvm vendor/bin/hhast-lint

.travis.yml

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+language: php
+php:
+ - hhvm
+ - hhvm-nightly
+matrix:
+  allow_failures:
+  - php: hhvm-nightly
+script:
+ - ./.travis.sh

CODE_OF_CONDUCT.md

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+# Code of Conduct
+
+Facebook has adopted a Code of Conduct that we expect project participants to adhere to.
+Please read the [full text](https://code.fb.com/codeofconduct/)
+so that you can understand what actions will and will not be tolerated.

CONTRIBUTING.md

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+# Contributing to DiffLib
+
+We want to make contributing to this project as easy and transparent as
+possible.
+
+## Code of Conduct
+The code of conduct is described in [`CODE_OF_CONDUCT.md`](CODE_OF_CONDUCT.md).
+
+## Our Development Process
+
+We develop on master, and make releases on an as-needed basic - usually
+to support new HHVM releases.
+
+## Pull Requests
+We actively welcome your pull requests.
+
+1. Fork the repo and create your branch from `master`.
+2. If you've added code that should be tested, add tests.
+3. If you've changed APIs, update the documentation.
+4. Ensure the test suite passes.
+5. Make sure your code lints.
+6. If you haven't already, complete the Contributor License Agreement ("CLA").
+
+## Contributor License Agreement ("CLA")
+In order to accept your pull request, we need you to submit a CLA. You only need
+to do this once to work on any of Facebook's open source projects.
+
+Complete your CLA here: <https://code.facebook.com/cla>
+
+## Issues
+We use GitHub issues to track public bugs. Please ensure your description is
+clear and has sufficient instructions to be able to reproduce the issue.
+
+Facebook has a [bounty program](https://www.facebook.com/whitehat/) for the safe
+disclosure of security bugs. In those cases, please go through the process
+outlined on that page and do not file a public issue.
+
+## Coding Style  
+* 2 spaces for indentation rather than tabs
+* 80 character line length
+* Match hackfmt output
+* Pass the configured HHAST linters
+
+## License
+By contributing to DiffLib, you agree that your contributions will be licensed
+under the LICENSE file in the root directory of this source tree.

LICENSE

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+MIT License
+
+Copyright (c) 2017-present, Facebook, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# DiffLib
+
+DiffLib is a Hack library for creating and parsing diffs. Diffs can be created
+between any two sequences of items. Additional helpers (such as support for
+unified diffs, and colored diffs) are provided for string diffs.
+
+Diffs are represented as a sequence of `DiffOp` operations; these can 'keep' an
+element (i.e. it's unchanged in both sequences), insert an element, or delete an
+element. For example, in a unified diff, these would be:
+
+```diff
+  DiffKeepOp
+- DiffDeleteOp
++ DiffInsertOp
+```
+
+String diffs are typically represented as a sequence of lines, but can also be
+represented as a sequence of characters, allowing intra-line diffs.
+
+## Examples
+
+```Hack
+use namespace Facebook\DiffLib;
+
+function create_unified_diff(string $from, string $to): string {
+  return DiffLib\StringDiff::lines($from, $to)->getUnifiedDiff();
+}
+
+function create_colored_diff(string $from, string $to): string {
+  return DiffLib\CLIColoredUnifiedDiff::create($from, $to);
+}
+
+final class IntDiff extends DiffLib\Diff {
+  const type TContent = int;
+}
+
+function dump_int_diff(vec<int> $from, vec<int> $to): void {
+  $diff = (new IntDiff($from, $to))->getDiff();
+  foreach ($diff as $op) {
+    if ($op is DiffLib\DiffKeepOp<_>) {
+      \printf("  %d\n", $op->getContent());
+    } else if ($op is DiffLib\DiffDeleteOp<_>) {
+      \printf("- %d\n", $op->getContent());
+    } else {
+      $op = $op as DiffLib\DiffInsertOp<_>;
+      printf("+ %d\n", $op->getContent());
+    }
+  }
+}
+
+```
+
+`dump_int_diff(vec[1, 3, 9], vec[1, 4, 9])` will produce this output:
+
+```
+  1
+- 3
++ 4
+  9
+```
+
+## Requirements
+
+* The current release version of HHVM
+
+## Installing DiffLib
+
+```
+composer require facebook/difflib
+```
+
+## How DiffLib works
+
+Diffs are created using Myers' diff algorithm:
+Myers, E.W. Algorithmica (1986) 1: 251. https://doi.org/10.1007/BF01840446
+
+For more details, see [the commented implementation](src/Diff.php).
+
+## Full documentation
+
+- `DiffLib\Diff`: abstract base class. Needs to be subclassed to operate on
+  any particular type.
+- `DiffLib\StringDiff`: final class for diffing strings, and adds support
+  for creating unified diffs
+- `DiffLib\ColoredUnifiedDiff`: abstract class for rendering unified diffs.
+  Output may be any type - for example, strings or XHP.
+- `DiffLib\CLIColoredUnifiedDiff`: abstract final class for rendering unified
+  diffs to a terminal that supports color escape sequences. Provides intra-line
+  highlighting.
+- `DiffLib\DiffOp`: abstract class for a diff operation. Sealed to
+  `DiffInsertOp`, `DiffKeepOp`, and `DiffDeleteOp`.
+- `DiffLib\cluster()`: utility function to group together sequential operations
+  of the same kind. Converts `vec<DiffOp<T>>` to a generally shorter number of
+  `vec<DiffOp<vec<T>>>`
+
+## License
+DiffLib is MIT licensed, as found in the LICENSE file.

composer.json

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+{
+    "name": "facebook/difflib",
+    "license": "MIT",
+    "require": {
+        "hhvm/hsl": "^3.28"
+    },
+    "require-dev": {
+        "hhvm/hhast": "^3.28"
+    }
+}