create main4
git commit -m 'main4'
git branch -m master mainline
+git branch subdir
git fetch ../subproj sub1
git branch sub1 FETCH_HEAD
-git subtree add --prefix=subdir FETCH_HEAD
+git subtree add --prefix=subdir/ FETCH_HEAD
# this shouldn't actually do anything, since FETCH_HEAD is already a parent
git merge -m 'merge -s -ours' -s ours FETCH_HEAD
git commit -m 'sub9'
cd ../mainline
-split2=$(git subtree split --annotate='*' --prefix subdir --rejoin)
+split2=$(git subtree split --annotate='*' --prefix subdir/ --rejoin)
git branch split2 "$split2"
create subdir/main-sub10