The ornamental design for a headcover with ponytailhole, as shown and described.
FIG. 1 is a front view of a head cover with ponytail hole of the present design;
FIG. 2 is a rear view of the design in FIG. 1;
FIG. 3 is a side view of the design in FIG. 1;
FIG. 4 is another side view of the design in FIG. 1; and,
FIG. 5 is a top view of the design in FIG. 1.
The broken lines showing a woman's head, neck, and ponytail in the drawings illustrate the claimed design while being worn, and form no part of the claim. The single broken line occurring around the opening for the wearer's eyes is stitching, and does not form a part of the claimed design.