There would have been a significant improvement in the clothing of the
Continental soldier in the winter of 1778-79 from that which was seen
at Valley Forge.
Head Quarters, Fredericksburgh, October 28, 1778.
Dear Sir: Part of the Cloathing has already arrived from Springfield and I imagine a sufficiency for the Troops in this quarter will be here in a day or two. I therefore desire you will immediately send up proper Officers from each of the Virginia Regiments and from the Delaware Regt. to draw their proportions. The Officers are to call at Head Quarters where they will receive orders upon the Deputy Cloathier for their uniforms compleat and for a proportion of Hatts and Blanketts. Be pleased to give notice to the commanding Officer of Genl. Woodfords Brigade.
-Ltr of Genl. Washington to Genl. Muhlenberg.
In 1778, the Virginia Brigades, Muhlenberg's Brigade (1st, 5th, 9th, and 13th Virginia and the German Regiment) Weedon's (2d, 6th, 10th, and 14th Virginia and Stewart's Penna State Regt) received a number of uniform coats manufactured in France. This was very probably the best equipped these troops would be for the entirety of the conflict. Twelve wagonloads of these coats arrived from ports in New England, whereafter, commonly referred to as French Bounty or Lottery coats, they were distributed based on the results of two lotteries held on October 28th. In the first lottery, Virginia and Delaware troops (Lot 2) drew brown faced red, in the second, blue faced red, there being a greater quantity of that color.
On the same day, several wagon loads of clothes also came from Williamsburg and the public stores of Virginia. They contained, among numerous bales of linen, 1903 green cloth breeches, 291 red serge breeches, 784 red flannel waistcoats, 435 red cloth (wool) waistcoats, and 492 red serge waist coats. It is possible that these state supplied bales of linen were made into overalls at the recommendation of Washington and in concordance with the January 1778 Congressional clothing warrant.
Dug buttons from a Virginia Brigade camp in the New Jersey Highlands
Given the time period associated with these encampments, these may
have been from the 1778 French Lottery coats and Public Store shipments.
According to Calver,
"...the most common type of Continental button is the one which bears the letters 'U.S.A.' Although we do not know exactly when this type was introduced, we can reasonably say-considering the locations at which it has been found and the probable date of the first use of the initials 'U.S.A.'-that it did not make its appearance before 1777. The frequency with which this button is found, however, would indicate that its issue was very general after that date..." 
French two piece buttons, from the same dig. Possibly from a lottery coat?