cr: Print a list of closest matching targets when no match is found

tools/cr/cr/actions/builder.py

Index: tools/cr/cr/actions/builder.py
diff --git a/tools/cr/cr/actions/builder.py b/tools/cr/cr/actions/builder.py
index 74959afe627e5acf06f07b3e95f0979dc540e02f..286d2ec92e492ae538f9ba57e260a0d63dc8c9c2 100644
--- a/tools/cr/cr/actions/builder.py
+++ b/tools/cr/cr/actions/builder.py
@@ -4,6 +4,8 @@
 
 """A module for the Builder base class."""
 
+import difflib
+
 import cr
 
 
@@ -56,6 +58,11 @@ class Builder(cr.Action, cr.Plugin.Type):
     """Check if a target name is on the builder knows about."""
     return target_name in self.GetTargets(context)
 
+  @cr.Plugin.activemethod
+  def GuessTargets(self, context, target_name):
+    """Returns a list of closest matching targets for a named target."""
+    return difflib.get_close_matches(target_name, self.GetTargets(context))
+
 
 class SkipBuilder(Builder):
   """The "skip" version of a Builder, causes the build step to be skipped."""