Crank bolt broke on me so I had to do this roadside fix - this is after I tidied it up at campsite to be bit less ugly.
I have all photos - breakage, this fix and more permanent fix from bike shop on mastodon the thread
I once snapped the derailleur hanger but I had a chain breaker and a spare quick link with me so I converted it into single speed to get back home but I fitted the chain to a wrong cog on the rear cassette so it kept downshifting making the chain extremely tight so I took a twig and twisted it around the cassette to prevent the chain from jumping up. That got me back home 15km away.