git-merge-file

git merge-file [-L [-L [-L ]]] [-p | --diff3 | --original] [--union] [-q | --quiet] [--marker-size=] [--]

-L
    Use specified labels instead of file names for conflict markers. Up to three labels can be given for , , and respectively.

-p
--diff3
    Show a diff3 style merge, meaning the base version content is shown in the middle of conflict markers.

--original
    Similar to --diff3, but includes information about the original source in the conflict header.

--union
    Do not generate conflict markers. Instead, add the conflicting lines from all participants to the output, which may result in uncompilable code.

-q
--quiet
    Suppress diagnostic output when conflicts occur.

--marker-size=
    Specify the number of '#' characters used in conflict markers. The default is 7.

--
    Marks the end of options; treats subsequent arguments as file names, useful if file names start with '-'.


    The 'ours' version of the file (the one being merged into). The result of the merge is written to this file.


    The common ancestor of and .


    The 'theirs' or 'remote' version of the file.

git-merge-file is a low-level Git command that performs a 3-way merge on three provided files: a common base version, the 'ours' version, and the 'theirs' (or 'remote') version. It is a fundamental component used internally by Git's higher-level merge mechanisms, such as git merge.

The command takes these three file paths as arguments and attempts to combine their changes into a single output file, typically written to the 'ours' file. If conflicts occur where changes overlap, git-merge-file inserts conflict markers into the output, allowing the user to resolve them manually. This tool is rarely invoked directly by end-users but is crucial for understanding how Git resolves divergences between branches.

Plumbing Command: git-merge-file is a plumbing command; it operates directly on file paths and does not interact with the Git index or repository history. Users rarely invoke this command directly.

Textual Merges Only: This command only handles textual merges. For binary files, Git's higher-level merge tools typically defer to specific binary merge strategies or signal a conflict.

git-merge-file employs a line-based merge strategy. It identifies common lines, insertions, and deletions between the three versions to produce the merged output. It's designed to be robust against various changes like line endings and whitespace differences (though it doesn't automatically normalize them).

When conflicts occur, the output file will contain special markers indicating the conflicted regions. The default markers typically look like:

<<<<<<< HEAD
    content from current-file
=======
    content from other-file
>>>>>>> branch-name

<<<<<<< HEAD
    content from current-file
||||||| base-file
    content from base-file
=======
    content from other-file
>>>>>>> branch-name

git-merge-file has been a core component of Git since its early days, predating many of the higher-level porcelain commands. It implements the standard 3-way merge algorithm, which is a foundational concept in version control systems. Its existence as a separate, low-level command allows Git to modularize its merge logic, making it robust and reusable.

git-merge(1), git-diff(1), git-rebase(1)