Added an help command to dump all options for completion

`bazel help completion` dump all options completion pattern
for each command, giving hints on the format of the completion
residue (e.g., `label`, `path`, `{a,enum}`, ...). This
dump can be used to generate completion scripts.

--
MOS_MIGRATED_REVID=90743024

1 files changed, 9 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/runtime/Command.java b/src/main/java/com/google/devtools/build/lib/runtime/Command.java
index 1797cd3b46..318e3e419b 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/Command.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/Command.java
@@ -105,4 +105,13 @@ public @interface Command {
    */
   boolean canRunInOutputDirectory() default false;
 
+  /**
+   * Returns the type completion help for this command, that is the type arguments that this command
+   * expects. It can be a whitespace separated list if the command take several arguments. The type
+   * of each arguments can be <code>label</code>, <code>path</code>, <code>string</code>, ...
+   * It can also be a comma separated list of values, e.g. <code>{value1,value2}<code>. If a command
+   * accept several argument types, they can be combined with |, e.g <code>label|path</code>.
+   */
+  String completion() default "";
+
 }