KEYCLOAK-5127: Exclude node_modules from git (keycloak#4334)

* KEYCLOAK-5127: Exclude node_modules from git

* Add readme file.

.gitignore

@@ -49,3 +49,7 @@ target
 # Maven shade
 #############
 *dependency-reduced-pom.xml
+
+# nodejs #
+##########
+node_modules

themes/pom.xml

@@ -50,5 +50,49 @@
             </build>
         </profile>
     </profiles>
+
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-clean-plugin</artifactId>
+                <configuration>
+                    <filesets>
+                        <fileset>
+                            <directory>src/main/resources/theme/keycloak/common/resources/node_modules</directory>
+                        </fileset>
+                    </filesets>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>com.github.eirslett</groupId>
+                <artifactId>frontend-maven-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>install node and yarn</id>
+                        <goals>
+                            <goal>install-node-and-yarn</goal>
+                        </goals>
+                        <phase>generate-resources</phase>
+                    </execution>
+                    <execution>
+                        <id>yarn install</id>
+                        <goals>
+                            <goal>yarn</goal>
+                        </goals>
+                        <phase>process-resources</phase>
+                        <configuration>
+                            <arguments>install --production=false --frozen-lockfile</arguments>
+                        </configuration>
+                    </execution>
+                </executions>
+                <configuration>
+                    <nodeVersion>v6.11.1</nodeVersion>
+                    <yarnVersion>v0.27.5</yarnVersion>
+                    <workingDirectory>src/main/resources/theme/keycloak/common/resources</workingDirectory>
+                    <installDirectory>target</installDirectory>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
 
 </project>

themes/src/main/resources/theme/keycloak/common/resources/README.md

@@ -0,0 +1,24 @@
+Management of javascript libraries
+===================================================
+
+Javascript libraries under the *./lib* directory are not managed.  These 
+libraries are not available in the public npm repo and are thus checked into 
+GitHub.
+
+Javascript libraries under *./node_modules* directory are managed with yarn.  
+THEY SHOULD NOT BE CHECKED INTO GITHUB!
+
+Adding or Removing javascript libraries
+---------------------------------------
+To add/remove/update javascript libraries you should always use yarn so that 
+the yarn.lock file will be updated.  Then, just check in the modified version 
+of package.json and yarn.lock.  To do this, you should locally install 
+nodejs/npm and yarn.
+
+Do not use *npm install --save*. If you try to update a dependency using 
+package.json and fail to update yarn.lock, then the next build will fail.
+
+To locally install nodejs/npm and yarn, see:
+
+* [Install nodejs and npm](https://www.npmjs.com/get-npm)
+* [Install yarn](https://yarnpkg.com/lang/en/docs/install/)