Migration notes from 0.0.14 to 0.1.0 (#154)

* Migration notes from 0.0.14 to 0.1.0

* docs: suggestion improvements

* docs: remove trailing ##

* docs: mention new classpath/module path behavior

* docs: expand migration docs on variant problems

* docs: split migration into sub sections

* docs: move before/after to before note on extra-java-module-info plugin

* docs: incorporating suggestions

* docs: incorporating suggestions

* docs: add notes on dependency hierarchy changes

* docs: typo fix

Author: samypr100

README.md

@@ -199,9 +199,131 @@ javafx {
 }
 </code></pre>
 
-## Issues and Contributions ##
+## Issues and Contributions
 
 Issues can be reported to the [Issue tracker](https://github.com/openjfx/javafx-gradle-plugin/issues/).
 
 Contributions can be submitted via [Pull requests](https://github.com/openjfx/javafx-gradle-plugin/pulls/), 
 providing you have signed the [Gluon Individual Contributor License Agreement (CLA)](https://cla.gluonhq.com/).
+
+## Migrating from 0.0.14 to 0.1.0
+
+Version `0.1.0` introduced several changes and improvements, including lazy dependency declaration,
+variant-aware dependency management, and support for Gradle's built-in JPMS functionality. In the
+previous version, the classpath/module path was rewritten. This is no longer the case. As a result,
+your past builds might be affected when you upgrade the plugin. In the next section, there are a few
+troubleshooting steps that might help with the transition if you encounter issues when upgrading.
+These examples are provided on a best-effort basis, but feel free to open an issue if you believe
+there's a migration scenario not covered here that should be included.
+
+### Troubleshooting
+
+#### Gradle version
+
+The plugin now requires `Gradle 6.1` or higher. Consider updating your Gradle settings, wrapper,
+and build to a more recent version of Gradle. Additionally, updating your plugins and dependencies
+can help minimize issues with the plugin.
+
+#### Mixed JavaFX jars
+
+If you encounter mixed classified JavaFX jars or see errors like `Error initializing QuantumRenderer: no
+suitable pipeline found` during executing task like `build`, `test`, `assemble`, etc., it is likely one
+or more of your dependencies have published metadata that includes JavaFX dependencies with classifiers.
+The ideal solution is to reach out to library authors to update their JavaFX plugin and publish a patch
+with fixed metadata. A fallback solution to this is to `exclude group: 'org.openjfx'` on the dependencies
+causing the issue.
+
+```groovy
+implementation('com.example.fx:foo:1.0.0') {
+    exclude group: 'org.openjfx', module: '*'
+}
+```
+
+#### Variants
+
+If you encounter errors such as `Cannot choose between the following variants of org.openjfx...` it is possible
+that your build or another plugin is interacting with the classpath/module path in a way that "breaks" functionality
+provided by this plugin. In such cases, you may need to re-declare the variants yourself as described in [Gradle docs
+on attribute matching/variants](https://docs.gradle.org/current/userguide/variant_attributes.html) or reach out to
+the plugin author in an attempt to remediate the situation.
+
+```groovy
+// Approach 1: Explicit Variant
+// The following snippet will let you add attributes for linux and x86_64 to a configuration
+configurations.someConfiguration {
+    attributes {
+        attribute(Usage.USAGE_ATTRIBUTE, objects.named(Usage, Usage.JAVA_RUNTIME))
+        attribute(OperatingSystemFamily.OPERATING_SYSTEM_ATTRIBUTE, objects.named(OperatingSystemFamily, "linux"))
+        attribute(MachineArchitecture.ARCHITECTURE_ATTRIBUTE, objects.named(MachineArchitecture, "x86-64"))
+    }
+}
+
+// Approach 2: Copy existing configuration into another configuration
+configurations.someConfiguration  {
+    def runtimeAttributes = configurations.runtimeClasspath.attributes
+    runtimeAttributes.keySet().each { key ->
+        attributes.attribute(key, runtimeAttributes.getAttribute(key))
+    }
+}
+```
+
+#### Extra plugins
+
+In versions `0.0.14` and below, there was a transitive dependency on `org.javamodularity.moduleplugin`.
+If your **modular** project stops working after updating to `0.1.0` or above, it is likely that you need to
+explicitly add the [org.javamodularity.moduleplugin](https://plugins.gradle.org/plugin/org.javamodularity.moduleplugin)
+back to your build and set `java.modularity.inferModulePath.set(false)` to keep things working as they were.
+This plugin helped with transitive dependencies on legacy jars that haven't been modularized yet, but now you
+have to option choose which approach to take. This change should not be required for non-modular projects.
+
+**Before**
+
+````groovy
+plugins {
+    id 'org.openjfx.javafxplugin' version '0.0.14'
+}
+````
+
+**After**
+
+````groovy
+plugins {
+    id 'org.openjfx.javafxplugin' version '0.1.0'
+    id 'org.javamodularity.moduleplugin' version '1.8.12'
+}
+
+java {
+    modularity.inferModulePath.set(false)
+}
+````
+
+**Note**: There are other recommended alternatives over `org.javamodularity.moduleplugin` for modular projects such as
+[extra-java-module-info](https://github.com/gradlex-org/extra-java-module-info) that would allow you to keep
+`inferModulePath` set to **true** by declaring missing module information from legacy jars. More details on how to
+accomplish can be found on the plugin's source code repository.
+
+#### Dependency hierarchy
+
+Version `0.1.0` now relies on JavaFX modules defining their transitive modules rather than flattening them.
+This change allows you to publish metadata declaring only the JavaFX modules you need, meaning it does not
+include transitive JavaFX modules as part of your published metadata.
+
+Some plugins rely on having all modules (transitive included) declared as "top-level" modules such as the
+`badass-runtime-plugin` on **non-modular** projects. In this particular case, it is necessary to declare
+all modules to restore previous functionality from `0.0.14` and below.
+
+**Before**
+
+````groovy
+javafx {
+    modules = ['javafx.controls']
+}
+````
+
+**After**
+
+````groovy
+javafx {
+    modules = ['javafx.base', 'javafx.graphics', 'javafx.controls']
+}
+````