I am issuing these:
git format-patch 2f3e744 2f3e744^
or
git format-patch 2f3e744..3e853
In the latter, 3e853 is a commit earlier than 2f3e744.
Neither command resulted in some change (not the result I was expecting).
My goal is to make a patch based on changes from revision 3e853.
You're subject is actually wrong. You're command line is not providing that, it's providing ^2f3e744 3e853, which excludes your commit. The proper way to write this is git format-patch 3e853..2f3e744. You could also do:
git format-patch -1 3e853 - Which means take 1 commit starting at 3e853.git format-patch 3e853 '^3e853^' - Which means taken the set the leads up to 3e853, and subtract out everything before it. Note the quotes. Some shells will try to interpret the carets (^), so you may need them.The git rev-list docs are a good resource for this information.
Update: You're title changed, it's the first example now. And it may not be producing anything because your history is short. I'd expect the first command to emit a patch for everything up to 2f3e744.