[MNGSITE-414] clean up https /maven.apache.org/configure.html

content/markdown/configure.md

@@ -17,42 +17,107 @@ KIND, either express or implied.  See the License for the
 specific language governing permissions and limitations
 under the License.
 -->
-The configuration for Apache Maven usage itself and projects built with resides 
-in a number of places: 
 
-## `MAVEN_OPTS` environment variable:
+Apache Maven ships with two launcher commands in the `${MAVEN_HOME}/bin` folder,
+which - based on several environment variables, project files and system files as described below
+- constructs and runs the appropriate `java ...` command line which then invokes the Java Virtual Machine (JVM) 
+that actually runs Maven.
 
-This variable contains parameters used to start up the JVM running Maven and
-can be used to supply additional options to it. E.g. JVM memory
-settings could be defined with the value `-Xms256m -Xmx512m`.
+* `mvn` - normal way to run from the command line.
+* `mvnDebug` - launches `mvn` in debug mode, waiting for a Java debugger to attach to port `$MAVEN_DEBUG_ADDRESS` (default 8000).
 
-## `MAVEN_ARGS` environment variable:
+
+## Environment variables
+
+In the following the Unix syntax for environment variables is used in the text.
+
+For Windows the syntax is slightly different, for `$A` use `%A%`.
+
+### `$MAVEN_OPTS` - `%MAVEN_OPTS%`
+
+The contents of this variable is placed in the `java` command _before_ the class name, and 
+can therefore be used to provide additional arguments to the Java Virtual Machine (JVM) without
+having to specify them on the command line every time.
+
+Examples include garbage collector and memory configuration, but _not_ options to Maven itself
+
+Use `java --help` and `java -X` to see what is possible in this particular JVM.
+
+<!--
+### `$MAVEN_ARGS`
 
 Starting with Maven 4, this variable contains arguments passed to Maven before
 CLI arguments. E.g., options and goals could be defined with the value
 `-B -V checkstyle:checkstyle`.
+-->
+
+### `$MAVEN_BASEDIR` - `%MAVEN_BASEDIR%`
+
+If set, this is considered the base directory of the Maven project.  If not set, 
+the launcher scripts search for a `.mvn` folder towards the root of the drive, and if
+found consider that the base directory.
+
+
+### `$MAVEN_SKIP_RC` - `%MAVEN_SKIP_RC%`
+
+If set, tells the launcher scripts _not_ to read the various Maven configuration files.
+This is useful to get standard behaviour.
+
+### `$JAVA_HOME` - `%JAVA_HOME%`
+
+If set, the Java binary to be used must be found at `$JAVA_HOME/bin/java` or an error will
+be reported.  If not set, the Java binary is found in the `$PATH`.
+
+### `$MAVEN_DEBUG_OPTS` - `%MAVEN_DEBUG_OPTS%`
+
+Additional options for the JVM if needed.  
+They are put after `$MAVEN_OPTS` and before the `-classpath` argument.
+
+## Files
 
-## `settings.xml` file:
+Files in `$MAVEN_BASEDIR` and below are part of your project and may be checked 
+into source control.
 
-Located in USER_HOME/.m2 the settings files is designed to contain any
-configuration for Maven usage across projects.
+### `$USER/.m2/settings.xml` - `%USER_HOME%\.m2\settings.xml`
 
-## `.mvn` directory:
+This contains the user-specific Maven setup used across projects.  
+Often this is used to tell Maven to use an internal repository instead of Maven Central if behind a firewall, 
+various profiles, and passwords.
 
-Located within the project's top level directory, the files `maven.config`, `jvm.config`, and `extensions.xml`
-contain project specific configuration for running Maven.
+<!-- 
 
-This directory is part of the project and may be checked in into your version control.
+### `$MAVEN_BASEDIR/.mvn/maven.config`:
 
-### `.mvn/extensions.xml` file:
+FIXME:  IS THIS STILL THE CASE? LAUNCHER SCRIPTS DOES NOT LOOK FOR IT?!?
 
-The old way (up to Maven 3.2.5) was to create a jar (must be shaded if you have other dependencies) which contains the extension and put 
-it manually into the `${MAVEN_HOME}/lib/ext` directory. This means you had to change the Maven installation. The consequence was that everyone
-who likes to use this needed to change it’s installation and makes the on-boarding for a developer much more inconvenient. The other 
-option was to give the path to the jar on command line via `mvn -Dmaven.ext.class.path=extension.jar`. This has the drawback giving those 
-options to your Maven build every time you are calling Maven. Not very convenient as well.
+This file contains additional command line arguments added to every invocation of Maven.
+
+For example things like `-T3 -U --fail-at-end`. 
+So you only have to call Maven just by using `mvn clean package` 
+instead of `mvn -T3 -U --fail-at-end clean package`.
+
+-->
+
+### `$MAVEN_BASEDIR/.mvn/jvm.config`:
+
+Allows a persistable alternative to `$MAVEN_OPTS` for providing 
+additional arguments to the JVM before the class name on the constructed 
+`java ...` command line.  Sample contents: 
+
+        -Xmx2048m -Xms1024m -XX:MaxPermSize=512m -Djava.awt.headless=true
+
+Word of caution:  If you for any reason need to configure memory usage or the garbage collector - which should
+be considered a last resort - be absolutely certain that the configuration you use 
+applies to the version of the JVM you are using, and that you understand what you are doing.
+
+
+### `$MAVEN_BASEDIR/.mvn/extensions.xml`
+
+FIXME:  WHERE IS THIS DONE?  IS THIS MAVEN 4 FUNCTIONALITY?
+
+If you for any reason needs additional artifacts put on the classpath used by Maven,
+simply list them here with their usual Maven coordinates.
 
-From now on this can be done much more simpler and in a more Maven like way. So you can define an `${maven.projectBasedir}/.mvn/extensions.xml` file which looks like the following:
 
 ```xml
 <extensions xmlns="http://maven.apache.org/EXTENSIONS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
@@ -65,26 +130,35 @@ From now on this can be done much more simpler and in a more Maven like way. So
 </extensions>
 ```
 
-Now you can simply use an extension by defining the usual maven coordinates groupId, artifactId, version as any other artifact. Furthermore all transitive dependencies of those extensions will automatically being downloaded from your repository. So no need to create a shaded artifact anymore.
+### `/usr/local/etc/mavenrc` + `/etc/mavenrc` + `$HOME/.mavenrc`
 
-### `.mvn/maven.config` file:
+Unix-like systems only: 
+Configuration files executed by the Unix launcher scripts first thing, unless
+if the environment variable `$MAVEN_SKIP_RC` is set.
 
-It’s really hard to define a general set of options for calling the maven command line. Starting with Maven 3.3.1+, this can be solved by 
-putting this 
-options to a script but this can now simple being done by defining `${maven.projectBasedir}/.mvn/maven.config` file which contains the 
-configuration options for the `mvn` command line. 
+Typically environment variables - including `$PATH` - are set here.
 
-For example things like `-T3 -U --fail-at-end`. So you only have to call Maven just by using `mvn 
-clean package` instead of `mvn -T3 -U --fail-at-end clean package` and not to miss the `-T3 -U --fail-at-end` options on every call. The 
-`${maven.projectBasedir}/.mvn/maven.config` is located in the `${maven.projectBasedir}/.mvn/` directory; also works if in the root of a multi module build.
+### `%USERPROFILE%\mavenrc_pre.bat` + `%USERPROFILE%\mavenrc_pre.cmd`
 
-### `.mvn/jvm.config` file:
+Windows systems only:
+Configuration files executed by the Windows launcher scripts first thing _before_ launching the Maven JVM, 
+unless if the environment variable `%MAVEN_SKIP_RC%` is set.
 
-Starting with Maven 3.3.1+ you can define JVM configuration via `${maven.projectBasedir}/.mvn/jvm.config` file which means you can define the options for your build on a per project base. This file will become part of your project and will be checked in along with your project. So no need anymore for `MAVEN_OPTS`, `.mavenrc` files. So for example if you put the following JVM options into the `${maven.projectBasedir}/.mvn/jvm.config` file
+This can be used to provide secrets, like the password for a keystore:
 
-        -Xmx2048m -Xms1024m -XX:MaxPermSize=512m -Djava.awt.headless=true
+```
+set MAVEN_OPTS=-Djavax.net.ssl.keyStore="<path to p12 file>" -Djavax.net.ssl.keyStoreType=pkcs12 -Djavax.net.ssl.keyStorePassword=<password>
+```
+
+### `%USERPROFILE%\mavenrc_post.bat` + `%USERPROFILE%\mavenrc_post.cmd`
+
+Windows systems only:
+Configuration files executed by the Windows launcher scripts _after_ the Maven JVM itself exits, unless
+if the environment variable `%MAVEN_SKIP_RC%` is set.
+
+
+---
 
-You don't need to use these options in `MAVEN_OPTS` or switch between different configurations.
 
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