Scenario: `main` is merged into a feature branch repeatedly

The same monorepo lines of work can meet more than once. This example starts with the merge from the folder's base scenario, then changes main, merges it into feature a second time, and adds one more feature commit.

git subtree split retains both merge edges and all commits from main. git-splice emits the first-parent story: each merge is one ordinary commit whose tree includes the newly merged content.

Output

setup.bash builds this state:

$ build_scenario scenario_merge_in_monorepo && merge_main_into_feature_again "$PWD"

The monorepo contains two merges from main:

$ git log --graph --format=%s | sed 's/ *$//'
* after the second merge
*   Merge branch 'main' into feature
|\
| * second main work
* | after the merge
* | Merge branch 'main' into feature
|\|
| * main work
* | feature work
|/
* add vendor/a
* initial commit

$ git subtree split --quiet --prefix=vendor/a --branch subtree-result >/dev/null && echo "created subtree-result"
created subtree-result

$ git log --graph --format=%s subtree-result | sed 's/ *$//'
* after the second merge
*   Merge branch 'main' into feature
|\
| * second main work
* | after the merge
* | Merge branch 'main' into feature
|\|
| * main work
* | feature work
|/
* add vendor/a

The splice rebuild is linear even after repeated merges:

$ git splice push vendor/a
??   vendor/a: upstream has no 'feature' branch yet -- this push creates it
ok   vendor/a: pushed d3cbcfa to feature

$ git -C "$UPSTREAM" log --graph --format=%s feature
* after the second merge
* Merge branch 'main' into feature
* after the merge
* Merge branch 'main' into feature
* feature work
* seed

Output​

Output