What is a good utility for trimming .dv files without losing metadata?
The following ffmpeg command will remove the first and last minute of a ten-minute input file:

ffmpeg -i input.avi -ss 00:01:00 -t 00:08:00 -c copy output.avi


-ss means start seek; that is, where the output will begin. -t means time; that is, the length of the output: so the above command will start at the first minute, and end eight minutes later.

With some video codecs, using these options with -c copy can cause issues due to I-frames (i.e. ffmpeg will cut to the nearest I-frame). This shouldn't be a problem with DV, though, sine AFAIK it's I-frame only.