git-merge-tree
Combine and analyze content differences between trees
TLDR
Show the result of a merge between two branches
Perform a merge and write the resulting tree
SYNOPSIS
git merge-tree [--write-tree] <base-tree> [-X<strategy-option>=<value>...] <head> <remote> [--] [<pathspec>...]
PARAMETERS
--write-tree
Output the ID of the resulting tree object to stdout instead of per-path contents.
-X<option>=<value>, --strategy-option=<option>=<value>
Pass the specified merge strategy option and value (e.g., -Xpatience).
DESCRIPTION
git merge-tree is a low-level plumbing command in Git that performs a three-way merge between a base tree, head tree, and remote tree for specified paths. Unlike higher-level commands like git merge, it does not modify the working directory, index, or repository state. Instead, it outputs the merge results directly to stdout.
For each pathspec, if the merge is clean, it prints the path followed by a NUL byte and the merged blob content. In case of conflicts, it outputs a detailed conflict format with markers:
path
<<<<<<< HEAD
head content
||||||| base
base content
=======
remote content
>>>>>>> remote
This makes it ideal for scripting merge resolution, inspecting potential conflicts, or integrating into custom tools. It supports merge strategies via options, allowing customization like ignoring whitespace. Recent versions added --write-tree to output the resulting tree object ID, enabling efficient merge tree creation without full checkout.
Primarily used internally by Git porcelain commands, it's valuable for advanced users needing precise control over tree merges.
CAVEATS
Plumbing command: output format not guaranteed stable across Git versions. Does not recurse into submodules. Requires tree-ish arguments (commits, trees, tags). Paths with conflicts include full markup; clean merges use NUL-separated binary output.
OUTPUT FORMAT
Clean merge: <path>NULmerged-content
Conflict: <path>
<<<<<<< head-label
head content
||||||| base-label
base content
=======
remote content
>>>>>>> remote-label
HISTORY
Added in Git 1.7.4 (April 2011) as plumbing for tree-level merges. The --write-tree option introduced in Git 2.46 (July 2024) to support efficient scripted merging without index manipulation.
SEE ALSO
git-merge(1), git-merge-file(1), git-read-tree(1), git-write-tree(1)
