The common shirt of the 18th century was a pullover type shirt, open at the neck or just one button at the collar. The common work frock of the time was made on the same pattern, and sometimes refered to as a hunting shirt. The shirt should be knee length or longer. When wearing breeches, the shirt was tucked between the legs.
Detail of an original shirt. This shows the neck opening, the collar and the gathering at the top of the sleeve.
Detail of the placket, the lower part of the neck opening.
The gathering of the top of the sleeve at the shoulder.
Cuff detail on the sleeve.
This shot is taken from a video, and it is not very clear. But it does show the join of the sleeve, where it is gathered, sits just below the shoulder not at the top like modern shirts.
This shows the placket on my frock which is made on the same pattern as the common shirt.
Full in the sleeve, plenty of room to move. Length at least to the knees. This is the type of frock I believe Daniel Day Lewis is wearing in The Last Of The Mohicans Crying Wolf.