+#!/bin/bash -x
+. shellopts.sh
+set -e
+
+rm -rf mainline subproj
+mkdir mainline subproj
+
+cd subproj
+git init
+
+touch sub1
+git add sub1
+git commit -m 'sub-1'
+git branch sub1
+git branch -m master subproj
+
+touch sub2
+git add sub2
+git commit -m 'sub-2'
+git branch sub2
+
+touch sub3
+git add sub3
+git commit -m 'sub-3'
+git branch sub3
+
+cd ../mainline
+git init
+touch main1
+git add main1
+git commit -m 'main-1'
+git branch -m master mainline
+
+git fetch ../subproj sub1
+git branch sub1 FETCH_HEAD
+git read-tree --prefix=subdir FETCH_HEAD
+git checkout subdir
+git commit -m 'initial-subdir-merge'
+
+git merge -m 'merge -s -ours' -s ours FETCH_HEAD
+
+touch subdir/main-sub3
+git add subdir/main-sub3
+git commit -m 'main-sub3'
+
+touch main-2
+git add main-2
+git commit -m 'main-2 boring'
+
+touch subdir/main-sub4
+git add subdir/main-sub4
+git commit -m 'main-sub4'
+
+git fetch ../subproj sub2
+git branch sub2 FETCH_HEAD
+git merge -s subtree FETCH_HEAD
+git branch pre-split
+
+split1=$(git subtree split --onto FETCH_HEAD subdir --rejoin)
+echo "split1={$split1}"
+git branch split1 "$split1"
+
+touch subdir/main-sub5
+git add subdir/main-sub5
+git commit -m 'main-sub5'
+
+cd ../subproj
+git fetch ../mainline split1
+git branch split1 FETCH_HEAD
+git merge FETCH_HEAD
+
+touch sub6
+git add sub6
+git commit -m 'sub6'
+
+cd ../mainline
+split2=$(git subtree split subdir --rejoin)
+git branch split2 "$split2"
+
+touch subdir/main-sub7
+git add subdir/main-sub7
+git commit -m 'main-sub7'
+
+split3=$(git subtree split subdir --rejoin)
+git branch split3 "$split3"
+
+cd ../subproj
+git fetch ../mainline split3
+git branch split3 FETCH_HEAD
+git merge FETCH_HEAD
+git branch subproj-merge-split3
+
+cd ../mainline
+git fetch ../subproj subproj-merge-split3
+git branch subproj-merge-split3 FETCH_HEAD
+git merge subproj-merge-split3