Shares of Dollar General (DG -3.66%) were moving lower today, even though there was no company-specific news out on the discount retailer. Instead, the move seemed to come in response to disappointing results from Target (TGT -21.07%) this morning, which seemed to confirm that Walmart (WMT 0.27%), which reported earnings yesterday, is continuing to gobble up market share from competitors like Target and Dollar General.As of 1:19 p.m. ET, Dollar General stock was down 4.5%. Dollar General's weakness continue ...