Add documentation for InjectSemanticdbOptions

Author: olafurpg

semanticdb-javac/src/main/java/com/sourcegraph/semanticdb_javac/InjectSemanticdbOptions.java

@@ -7,6 +7,31 @@
 import java.util.List;
 
 public class InjectSemanticdbOptions {
+  /**
+   * Updates a list of Java compiler arguments to include -Xplugin:semanticdb.
+   *
+   * This main method should be used by a `javac` wrapper script like this:
+   *
+   * <pre>
+   *     NEW_OPTIONS_PATH=$(mktemp)
+   *     java -cp semanticdb.jar \
+   *         -Dsemanticdb.output=NEW_OPTIONS_PATH \
+   *         com.sourcegraph.semanticdb_javac.InjectSemanticdbOptions $@
+   *     javac @$NEW_OPTIONS_PATH
+   * </pre>
+   *
+   * Requires the following system properties:
+   *
+   * <ul>
+   *     <li>-Dsemanticdb.output=PATH: the file to write the updated compiler options</li>
+   *     <li>-Dsemanticdb.old-output=PATH: the file to write the original compiler options. Only used for debugging purposes.</li>
+   *     <li>-Dsemanticdb.pluginpath=PATH: the path to the SemanticDB compiler plugin jar</li>
+   *     <li>-Dsemanticdb.sourceroot=PATH: the path to use in -Xplugin:semanticdb -sourceroot:PATH</li>
+   *     <li>-Dsemanticdb.targetroot=PATH: the path to use in -Xplugin:semanticdb -targetroot:PATH</li>
+   * </ul>
+   *
+   * @param args the Java compiler arguments to update.
+   */
   public static void main(String[] args) throws IOException {
     SemanticdbOptionBuilder newArgs = new SemanticdbOptionBuilder();
     for (String arg : args) {