Print out env variables in java format (#998)

* Print out env variables in java format

Print out JAVA_HOME and PATH variable in the google-java-format-diff.py script
immediately prior to running the underlying java program that does the actual
format checking.

* Use the java binary from JAVA_HOME for java-format

Use "$JAVA_HOME/bin/java" for invoking the java format check instead of
whatever version of java happens to be on the path.

* Removed unused import

java-format/google-java-format-diff.py

@@ -55,6 +55,8 @@ def main():
   parser.add_argument('-b', '--binary', help='path to google-java-format binary')
   parser.add_argument('--google-java-format-jar', metavar='ABSOLUTE_PATH', default=None,
                       help='use a custom google-java-format jar')
+  parser.add_argument('-j', '--java-binary', default='java',
+                      help='path to the java binary')
 
   args = parser.parse_args()
 
@@ -91,7 +93,7 @@ def main():
   if args.binary:
     base_command = [args.binary]
   elif args.google_java_format_jar:
-    base_command = ['java', '-jar', args.google_java_format_jar]
+    base_command = [args.java_binary, '-jar', args.google_java_format_jar]
   else:
     binary = find_executable('google-java-format') or '/usr/bin/google-java-format'
     base_command = [binary]

java-format/google-java-format-git-diff.sh

@@ -63,6 +63,7 @@ function callGoogleJavaFormatDiff() {
       showNoncompliantFiles "$forkPoint" "\033[1mNeeds formatting: "
       callResult=$(git diff -U0 ${forkPoint} | \
           ${SCRIPT_DIR}/google-java-format-diff.py \
+          --java-binary "$JAVA_HOME/bin/java" \
           --google-java-format-jar "${SCRIPT_DIR}/${JAR_NAME}" \
           -p1 | wc -l)
       ;;
@@ -70,12 +71,14 @@ function callGoogleJavaFormatDiff() {
       showNoncompliantFiles "$forkPoint" "\033[1mReformatting: "
       callResult=$(git diff -U0 ${forkPoint} | \
           ${SCRIPT_DIR}/google-java-format-diff.py \
+          --java-binary "$JAVA_HOME/bin/java" \
           --google-java-format-jar "${SCRIPT_DIR}/${JAR_NAME}" \
           -p1 -i)
       ;;
     "show")
       callResult=$(git diff -U0 ${forkPoint} | \
           ${SCRIPT_DIR}/google-java-format-diff.py \
+          --java-binary "$JAVA_HOME/bin/java" \
           --google-java-format-jar "${SCRIPT_DIR}/${JAR_NAME}" \
           -p1)
       ;;