I thought I knew enough git, but the other day I was still able to lose my changes...
Suppose I'm in master and already modified a file, and now I notice that it would be better to work on a devel branch with those changes, so I could pull upstream changes from master and merge locally. I think I did something like this:
git stash
git checkout -b devel
git stash apply
git add file.txt
git commit -m "XYZ new changes"
git checkout master
git fetch
git rebase origin/master (to avoid an empty merge, changes
upstream were in independent files)
git merge devel (to get commit "XYZ")