git-merge-tree

Show merge result

$ git merge-tree [base] [branch1] [branch2]

$ git merge-tree --write-tree [branch1] [branch2]

git merge-tree [options] base branch1 branch2

git merge-tree performs a three-way merge without touching the index or working tree. It shows what merge would produce, useful for previewing merges or scripted merge analysis.
The traditional mode requires specifying the base commit. Modern mode (--write-tree) automatically finds the merge base. It reports conflicts without actually merging.
git merge-tree enables merge preview and scripted merge testing.

BASE

Common ancestor commit.

First branch to merge.

Second branch to merge.

Modern mode: write result tree.

Only trivial merges.

Display help information.

Plumbing command. Output format varies by mode. Modern mode added in Git 2.38.

git merge-tree is a Git plumbing command enhanced in Git 2.38 with --write-tree mode for easier programmatic merge testing.

git-merge(1), git-merge-file(1)