Don't make len(p4Cmd("p4 changes -m 1 //foo/...")) == 0 succeed when the p4 command itself failed.

When the p4 command failed write out the exit code in the returned dict.

Signed-off-by: Simon Hausmann <shausman@trolltech.com>
diff --git a/contrib/fast-import/git-p4 b/contrib/fast-import/git-p4
index f12ad8b..89a85eb 100755
--- a/contrib/fast-import/git-p4
+++ b/contrib/fast-import/git-p4
@@ -31,7 +31,9 @@
             result.append(entry)
     except EOFError:
         pass
-    pipe.close()
+    exitCode = pipe.close()
+    if exitCode != None:
+        result["p4ExitCode"] = exitCode
 
     return result