Add `--is-draft` argument on patchset-created hook

The `--is-draft` argument will be passed with either `true` if
the patchset is a draft, or `false` otherwise.

This can be used by hooks that need to behave differently if the
change is a draft.

Change-Id: Idd00efe799bb05b0fd00e917faaccd5c772b1e1f
diff --git a/Documentation/config-hooks.txt b/Documentation/config-hooks.txt
index ef1c826..dfdba52 100644
--- a/Documentation/config-hooks.txt
+++ b/Documentation/config-hooks.txt
@@ -27,7 +27,7 @@
 changes and drafts).
 
 ====
-  patchset-created --change <change id> --change-url <change url> --project <project name> --branch <branch> --topic <topic> --uploader <uploader> --commit <sha1> --patchset <patchset id>
+  patchset-created --change <change id> --is-draft <boolean> --change-url <change url> --project <project name> --branch <branch> --topic <topic> --uploader <uploader> --commit <sha1> --patchset <patchset id>
 ====
 
 draft-published
diff --git a/gerrit-server/src/main/java/com/google/gerrit/common/ChangeHookRunner.java b/gerrit-server/src/main/java/com/google/gerrit/common/ChangeHookRunner.java
index dcc6701..37be293 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/common/ChangeHookRunner.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/common/ChangeHookRunner.java
@@ -232,6 +232,7 @@
 
         final List<String> args = new ArrayList<String>();
         addArg(args, "--change", event.change.id);
+        addArg(args, "--is-draft", patchSet.isDraft() ? "true" : "false");
         addArg(args, "--change-url", event.change.url);
         addArg(args, "--project", event.change.project);
         addArg(args, "--branch", event.change.branch);