Add developer info + sample config about how to work with a RAM disk

There are two files:
  - docs/developer/ram-disk/maven.config
  - docs/developer/ram-disk/settings-ramdisk.xml

The latter contains info about how to set up a development environment
inside a RAM disk. Both files are to be copied to the project's '.mvn'
folder in the root directory and adjusted according to the description.

Just in case, .gitignore ignores the files if they exist in '.mvn', so
they are not being staged and committed accidentally.

An additional screenshot shows how to configure the Windows Recycle Bin
to immediately delete files in order too save space on the RAM disk.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

3 files changed, 69 insertions, 0 deletions

diff --git a/docs/developer/ram-disk/maven.config b/docs/developer/ram-disk/maven.config
new file mode 100644
index 000000000..25f3d294d
--- /dev/null
+++ b/docs/developer/ram-disk/maven.config
@@ -0,0 +1 @@
+--settings R:/AspectJ/.mvn/settings-ramdisk.xml
diff --git a/docs/developer/ram-disk/settings-ramdisk.xml b/docs/developer/ram-disk/settings-ramdisk.xml
new file mode 100644
index 000000000..6957ca464
--- /dev/null
+++ b/docs/developer/ram-disk/settings-ramdisk.xml
@@ -0,0 +1,68 @@
+<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 https://maven.apache.org/xsd/settings-1.0.0.xsd">
+
+  <!--
+    RAM disk (RD) how-to:
+
+      1. Make sure the cloned project moves its local Git repository to a place outside the working directory on a
+         physical drive:
+           # Remove the "_" in between the two dashes in "-_-", two dashes are forbidden inside XML tags
+           git init -_-separate-git-dir=../MyProject.git
+         This ensures that your local Git commits are not lost if the computer reboots unexpectedly, even if you did not
+         push those commits to a remote yet. Ideally, make the Git repository directory a sibling right beside the
+         actual working directory and give it the same name as the workdir + ".git", as shown above.
+
+      2. Set up a RD, bind it to a drive letter (Windows) or mount it into an empty local folder (Linux, can also be
+         done on Windows). The RD should be big enough to house
+           - the project's working directory,
+           - all plugins, dependencies and artifacts needed and created by your Maven build,
+           - plus all the space needed during the build of your project for target folders, temporary files used while
+             creating assemblies or fat JARs, files created during tests etc.
+         On Windows, you might want to deactivate the Recycle Bin for the RAM disk drive. Screenshot
+         docs/developer/ram-disk/windows-recycle-bin-remove-immediately.png explains how to do that in English and
+         German.
+
+      3. Make sure to commit all your changes before shutting down the RD and/or the computer. You can skip that step
+         (at your own risk), if you make sure to save the RD contents to a shapshot file before unmounting.
+           - On Windows, products like Dataram RAMDisk (free up to 1 GB, needs licence otherwise, limited to a single
+             mounted RD) can do that for you. With RAMMap, you can mount any number of drives and have no size limit
+             (other than physical RAM), but have to save snapshots manually.
+           - On Linux, setting up a RD should be easy with on-board means. Mounting, unmounting and saving snapshots can
+             be done via start/stop scripts, which optionally can also be integrated into the Linux start-up and
+             shutdown processes. You could even regularly save snapshots using a cron job.
+
+      4. Copy the working directory to the root folder (e.g. R:/MyProject) of the RD and also create the base folder
+         specified here under "<localRepository>" for the local Maven repository.
+
+      5. Copy this file to <workdir>/.mvn/settings-ramdisk.xml.
+
+      6. Create a file <workdir>/.mvn/maven.config which will be found automatically by Maven - see
+         https://maven.apache.org/configure.html. Add this line, pointing Maven to this settings file with the
+         corresponding absolute path on your RD:
+           # Remove the "_" in between the two dashes in "-_-", two dashes are forbidden inside XML tags
+           -_-settings R:/MyProject/.mvn/settings-ramdisk.xml
+         Using relative paths will not work reliably, this Maven option will be added to each "mvn" call. So depending
+         on the current directory (e.g. submodule folder), you will get into trouble.
+
+      7. Download all plugins Maven needs and do a full build, checking if your RD is big enough:
+           mvn dependency:go-offline
+           mvn clean install
+
+      8. Enjoy, if the previous step was successful. Otherwise, start over with an increased RD size.
+
+      You may want to put .mvn/settings-ramdisk.xml and .mvn/maven.config on your project's .gitignore so as not to
+      commit them accidentally, if you or other project members do not permanently work with the RD or their
+      configuration differs. You may commit this file to another safe place in your project and put some information
+      into a development environment setup guide.
+  -->
+
+  <!-- Default - use if you want to switch to the default local Maven repo temporarily for some reason -->
+  <!--<localRepository>${user.home}/.m2/repository</localRepository>-->
+
+  <!-- RAM disk Windows -->
+  <localRepository>r:/.m2/repository</localRepository>
+
+  <!-- RAM disk Linux (Ubuntu via Windows Subsystem for Linux 2) -->
+  <!--<localRepository>/mnt/r/.m2/repository</localRepository>-->
+
+</settings>
diff --git a/docs/developer/ram-disk/windows-recycle-bin-remove-immediately.png b/docs/developer/ram-disk/windows-recycle-bin-remove-immediately.png
new file mode 100644
index 000000000..484bb7e25
--- /dev/null
+++ b/docs/developer/ram-disk/windows-recycle-bin-remove-immediately.png