...On my Revelate seatpost bag. I've tried folding it and tucking it in, but it still rubs on my leg when cycling. I don't want to cut it, in case I ever need it to be longer - maybe I'd like to bike swap.

Any recommendations on what to do?
agree that cutting your leg shorter is s bit extreme.
If you do cut your leg shorter can we have pics please?
Edit: You sure it’s not that huge arrow on the bag that’s chafing?
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why not tuck the excess into a small bag, maybe could hang it below the top-tube ?
I read that title with an extra ‘on’ ... an entirely different thread was expected 😊
Use the strap to retain something like a pump, therefore taking up some slack.
Just cut it. Then if you ever get a bike with thicker tubes, use a piece of double sided velcro to extend it or sew and extra bit on.
Helitape your leg.
Is that the Jerry can? Isn't there a loop on the other side to thread it through first?