TSK-1587: Pre-commit hook to ensure that all java files are formatted properly

.gitignore

@@ -64,3 +64,6 @@ Thumbs.db
 
 # jenv on mac
 /.java-version
+
+# java-format
+.java-format-cache

pom.xml

@@ -32,6 +32,7 @@
 
     <!-- build dependencies -->
     <version.checkstyle>8.41.1</version.checkstyle>
+    <version.google-java-format>1.10.0</version.google-java-format>
     <version.maven.checkstyle>3.1.2</version.maven.checkstyle>
     <version.maven.jar>3.2.0</version.maven.jar>
     <version.maven.compiler>3.8.1</version.maven.compiler>
@@ -98,6 +99,12 @@
         <type>pom</type>
         <scope>import</scope>
       </dependency>
+      <!-- Only necessary to automatically update the version for the pre-commit hook -->
+      <dependency>
+        <groupId>com.google.googlejavaformat</groupId>
+        <artifactId>google-java-format</artifactId>
+        <version>${version.google-java-format}</version>
+      </dependency>
     </dependencies>
   </dependencyManagement>
 

qa/hooks/pre-commit

@@ -0,0 +1,21 @@
+#!/bin/bash
+set -e # fail fast
+
+VERSION=$( [[ "$(grep "<version.google-java-format>" < "pom.xml")" =~ .*\>([^\<]+)\<.* ]] && echo "${BASH_REMATCH[1]}" )
+[[ -z "$VERSION" ]] && echo "Could not find version. Aborting commit." && exit 1
+
+REPOSITORY_URL="https://github.com/google/google-java-format/releases/download/v${VERSION}/"
+JAR_NAME="google-java-format-${VERSION}-all-deps.jar"
+JAR_DOWNLOAD_URL="$REPOSITORY_URL$JAR_NAME"
+
+CACHE_DIR=".java-format-cache"
+
+mkdir -p "$CACHE_DIR"
+[[ ! -f "$CACHE_DIR/$JAR_NAME" ]] && curl -LJf "$JAR_DOWNLOAD_URL" -o "$CACHE_DIR/$JAR_NAME"
+
+changed_java_files=$(git diff --cached --name-only --diff-filter=ACMR | grep ".*java$" || true)
+if [ -n "$changed_java_files" ]
+then
+  java -jar "$CACHE_DIR/$JAR_NAME" --replace --skip-sorting-imports $changed_java_files;
+  git add $changed_java_files;
+fi