PRG="$0"

# need this for relative symlinks
while [ -h "$PRG" ] ; do
  ls=`ls -ld "$PRG"`
  link=`expr "$ls" : '.*-> \(.*\)$'`
  if expr "$link" : '/.*' > /dev/null; then
    PRG="$link"
  else
    PRG="`dirname "$PRG"`/$link"
  fi
done

saveddir=`pwd`

MAVEN_HOME=`dirname "$PRG"`/..

# make it fully qualified
MAVEN_HOME=`cd "$MAVEN_HOME" && pwd`

set maven.conf default ${maven.home}/conf

[plexus.core]
load       ${maven.conf}/logging
optionally ${maven.home}/lib/ext/redisson/*.jar
optionally ${maven.home}/lib/ext/hazelcast/*.jar
optionally ${user.home}/.m2/ext/*.jar
optionally ${maven.home}/lib/ext/*.jar
load       ${maven.home}/lib/maven-*.jar

# For Cygwin and MinGW, switch paths to Windows format before running java(1) command
if $cygwin || $mingw ; then
  [ -n "$JAVA_HOME" ] &&
    JAVA_HOME=`cygpath --windows "$JAVA_HOME"`
  LAUNCHER_JAR=`cygpath --windows "$LAUNCHER_JAR"`
  CLASSWORLDS_CONF=`cygpath --windows "$CLASSWORLDS_CONF"`
  MAVEN_HOME=`cygpath --windows "$MAVEN_HOME"`
  MAVEN_PROJECTBASEDIR=`cygpath --windows "$MAVEN_PROJECTBASEDIR"`
fi

exec "$JAVACMD" \
  $MAVEN_OPTS \

@REM ==== START VALIDATION ====
if not "%JAVA_HOME%"=="" goto javaHomeSet
for %%i in (java.exe) do set "JAVACMD=%%~$PATH:i"
goto checkJavaCmd

:javaHomeSet
set "JAVACMD=%JAVA_HOME%\bin\java.exe"

if not exist "%JAVACMD%" (
  echo The JAVA_HOME environment variable is not defined correctly, so Apache Maven cannot be started. >&2
  echo JAVA_HOME is set to "%JAVA_HOME%", but "%%JAVA_HOME%%\bin\java.exe" does not exist. >&2
  goto error
)

        this.settingsBuilder = settingsBuilder;
    }

    public Settings buildSettings() throws IOException, XmlPullParserException {
        File userSettingsFile = getFile(
                "${user.home}/.m2/settings.xml", "user.home", MavenSettingsBuilder.ALT_USER_SETTINGS_XML_LOCATION);

        return buildSettings(userSettingsFile);
    }

 not sure the unified source directory structure addresses this issue.

 Properties

 maven.user.config.dir (system,default=${user.home}/.m2)
 maven.home            (system,user,default=${user.home}/m2)
 maven.repo.local      (system,user,default=${maven.user.config.dir}/repository)

 We need to define what happens in the when things are not setup correctly

:chkMHome
set "MAVEN_HOME=%~dp0"
set "MAVEN_HOME=%MAVEN_HOME:~0,-5%"
if "%MAVEN_HOME%"=="" goto error

:checkMCmd

  4) Make sure JAVA_HOME is set to the location of your JDK

  5) Run "mvn --version" to verify that it is correctly installed.

  For complete documentation, see https://maven.apache.org/download.html#Installation

  Licensing
  ---------

  Please see the file called LICENSE.

  Maven URLs
  ----------

  Home Page:          https://maven.apache.org/

KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
-->

<settings>
  <localRepository>${user.home}/.m2/repository</localRepository>

        tm1.addProvide("vendor", "sun");
        Xpp3Dom configuration1 = new Xpp3Dom("configuration");
        Xpp3Dom jdkHome1 = new Xpp3Dom("jdkHome");
        jdkHome1.setValue("${env.JAVA_HOME}");
        configuration1.addChild(jdkHome1);
        tm1.setConfiguration(configuration1);

        ToolchainModel tm2 = new ToolchainModel();
        tm1.setType("jdk");
        tm1.addProvide("version", "1.4");