bitbake: data_smart: VariableHistory: Ignore override duplicates and overlap with CoW functions

Trying to look up a variable called 'copy' in COW is problematic due
to internal implmentation details, at least avoid tracebacks from this.

Also don't duplicate override history (which is an atrefact of changed
override behaviour) as otherwise the bitbake -e output is convoluted.

(Bitbake rev: dddff5b7b8e6c18515b43389cef35503468b843d)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -231,6 +231,10 @@ class VariableHistory(object):
 
         if var not in self.variables:
             self.variables[var] = []
+        if not isinstance(self.variables[var], list):
+            return
+        if 'nodups' in loginfo and loginfo in self.variables[var]:
+            return
         self.variables[var].append(loginfo.copy())
 
     def variable(self, var):
@@ -460,6 +464,7 @@ class DataSmart(MutableMapping):
                 loginfo = event.copy()
                 loginfo['variable'] = shortvar
                 loginfo['op'] = 'override[%s]:%s' % (override, loginfo['op'])
+                loginfo['nodups'] = True
                 self.varhistory.record(**loginfo)
 
             override = None