Arbitrary rotation of symbols?

I have generated a shapefile of glacial lineations using a GIS, and have
successfully converted the line shapefile to GMT format using OGR. The
lineations plot fine in GMT.

These features are similar to vectors, in the sense that they illustrate
direction of flow, but they are different in that they are not described by a
length and azimuth as vectors are using -Sv; they curved lines. I want to show
the direction of flow by placing a triangle at the last x,y coordinate in the
line segment, but is it possible to rotate a triangle symbol so that the
triangle head is oriented correctly with respect to the trend of the line?

This is basically the same issue described in
https://listserv.hawaii.edu/cgi-bin/wa?A2=ind0801&L=GMT-HELP&P=R52411&1=GMT-HELP&9=A&I=-3&J=on&d=No+Match%3BMatch%3BMatches&z=4

but I'm not sure if the functionality has been added in the intervening 6
years. The psxy manual doesn't seem to indicate that there is, but I thought I
would ask anyway.

Thanks,

-- 
Eric Patton

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