Adding Churn PHP as a tool in the repo (#200)

## Description

Closes #68 

## Checklist
- [ ] Updated CHANGELOG files

.gitignore

@@ -12,3 +12,4 @@ composer.phar
 packages.json
 results.sarif
 infection.log
+.churn.cache

Makefile

@@ -4,6 +4,7 @@ PHP                 = php
 PHP_CS_FIXER        = tools/php-cs-fixer/vendor/bin/php-cs-fixer
 PHPUNIT             = tools/phpunit/vendor/bin/phpunit
 PSALM               = tools/psalm/vendor/bin/psalm
+CHURN               = tools/churn/vendor/bin/churn
 PSALM_BASELINE_FILE = psalm-baseline.xml
 BARD                = src/SonsOfPHP/Bard/bin/bard
 
@@ -200,9 +201,18 @@ infection:
 	-dapc.enable_cli=1 \
 	tools/infection/vendor/bin/infection --debug -vvv --show-mutations
 
-tools-install: psalm-install php-cs-fixer-install phpunit-install
+churn: ## Run Churn PHP
+	$(CHURN)
 
-tools-upgrade: psalm-upgrade php-cs-fixer-upgrade phpunit-upgrade
+churn-install:
+	$(COMPOSER) install --working-dir=tools/churn --no-interaction --prefer-dist --optimize-autoloader
+
+churn-upgrade:
+	$(COMPOSER) upgrade --working-dir=tools/churn --no-interaction --prefer-dist --optimize-autoloader --with-all-dependencies
+
+tools-install: psalm-install php-cs-fixer-install phpunit-install churn-install
+
+tools-upgrade: psalm-upgrade php-cs-fixer-upgrade phpunit-upgrade churn-upgrade
 
 ## Documentation
 docs-install: ## Install deps for building docs

churn.yml

@@ -0,0 +1,59 @@
+# The maximum number of files to display in the results table.
+# Default: 10
+filesToShow: 10
+
+# The minimum score a file need to display in the results table.
+# Disabled if null.
+# Default: 0.1
+minScoreToShow: 0
+
+# The command returns an 1 exit code if the highest score is greater than the threshold.
+# Disabled if null.
+# Default: null
+maxScoreThreshold: 0.9
+
+# The number of parallel jobs to use when processing files.
+# Default: 10
+parallelJobs: 10
+
+# How far back in the VCS history to count the number of commits to a file
+# Can be a human readable date like 'One week ago' or a date like '2017-07-12'
+# Default: '10 Years ago'
+commitsSince: One year ago
+
+# Files to ignore when processing. The full path to the file relative to the root of your project is required.
+# Also supports regular expressions.
+# Default: All PHP files in the path provided to churn-php are processed.
+#filesToIgnore:
+# - src/Commands/ChurnCommand.php
+# - src/Results/ResultsParser.php
+# - src/Foo/Ba*
+
+# File extensions to use when processing.
+# Default: php
+fileExtensions:
+ - php
+
+# This list is used only if there is no argument when running churn.
+# Default: <empty>
+directoriesToScan:
+ - src/
+
+# List of user-defined hooks.
+# They can be referenced by their full qualified class name if churn has access to the autoloader.
+# Otherwise the file path can be used as well.
+# See below the section about hooks for more details.
+# Default: <empty>
+#hooks:
+# - Namespace\MyHook
+# - path/to/my-hook.php
+
+# The version control system used for your project.
+# Accepted values: fossil, git, mercurial, subversion, none
+# Default: git
+vcs: git
+
+# The path of the cache file. It doesn't need to exist before running churn.
+# Disabled if null.
+# Default: null
+cachePath: .churn.cache

tools/churn/composer.json

@@ -0,0 +1,5 @@
+{
+    "require": {
+        "bmitch/churn-php": "^1.7"
+    }
+}