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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OUTPUT | EXIT STATUS | USAGE NOTES | INPUT FORMAT | MISTAKES TO AVOID | DEPRECATED DESCRIPTION | GIT | COLOPHON |
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GIT-MERGE-TREE(1) Git Manual GIT-MERGE-TREE(1)
git-merge-tree - Perform merge without touching index or working
tree
git merge-tree [--write-tree] [<options>] <branch1> <branch2>
git merge-tree [--trivial-merge] <base-tree> <branch1> <branch2> (deprecated)
This command has a modern --write-tree mode and a deprecated
--trivial-merge mode. With the exception of the DEPRECATED
DESCRIPTION section at the end, the rest of this documentation
describes the modern --write-tree mode.
Performs a merge, but does not make any new commits and does not
read from or write to either the working tree or index.
The performed merge will use the same features as the "real"
git-merge(1), including:
• three way content merges of individual files
• rename detection
• proper directory/file conflict handling
• recursive ancestor consolidation (i.e. when there is more than
one merge base, creating a virtual merge base by merging the
merge bases)
• etc.
After the merge completes, a new toplevel tree object is created.
See OUTPUT below for details.
--stdin
Read the commits to merge from the standard input rather than
the command-line. See INPUT FORMAT below for more information.
Implies -z.
-z
Do not quote filenames in the <Conflicted file info> section,
and end each filename with a NUL character rather than
newline. Also begin the messages section with a NUL character
instead of a newline. See OUTPUT below for more information.
--name-only
In the Conflicted file info section, instead of writing a list
of (mode, oid, stage, path) tuples to output for conflicted
files, just provide a list of filenames with conflicts (and do
not list filenames multiple times if they have multiple
conflicting stages).
--[no-]messages
Write any informational messages such as "Auto-merging <path>"
or CONFLICT notices to the end of stdout. If unspecified, the
default is to include these messages if there are merge
conflicts, and to omit them otherwise.
--quiet
Disable all output from the program. Useful when you are only
interested in the exit status. Allows merge-tree to exit early
when it finds a conflict, and allows it to avoid writing most
objects created by merges.
--allow-unrelated-histories
merge-tree will by default error out if the two branches
specified share no common history. This flag can be given to
override that check and make the merge proceed anyway.
--merge-base=<tree-ish>
Instead of finding the merge-bases for <branch1> and
<branch2>, specify a merge-base for the merge, and specifying
multiple bases is currently not supported. This option is
incompatible with --stdin.
As the merge-base is provided directly, <branch1> and
<branch2> do not need to specify commits; trees are enough.
-X<option>, --strategy-option=<option>
Pass the merge strategy-specific option through to the merge
strategy. See git-merge(1) for details.
For a successful merge, the output from git-merge-tree is simply
one line:
<OID of toplevel tree>
Whereas for a conflicted merge, the output is by default of the
form:
<OID of toplevel tree>
<Conflicted file info>
<Informational messages>
These are discussed individually below.
However, there is an exception. If --stdin is passed, then there
is an extra section at the beginning, a NUL character at the end,
and then all the sections repeat for each line of input. Thus, if
the first merge is conflicted and the second is clean, the output
would be of the form:
<Merge status>
<OID of toplevel tree>
<Conflicted file info>
<Informational messages>
NUL
<Merge status>
<OID of toplevel tree>
NUL
Merge status
This is an integer status followed by a NUL character. The integer
status is:
0: merge had conflicts
1: merge was clean
OID of toplevel tree
This is a tree object that represents what would be checked out in
the working tree at the end of git merge. If there were conflicts,
then files within this tree may have embedded conflict markers.
This section is always followed by a newline (or NUL if -z is
passed).
Conflicted file info
This is a sequence of lines with the format
<mode> <object> <stage> <filename>
The filename will be quoted as explained for the configuration
variable core.quotePath (see git-config(1)). However, if the
--name-only option is passed, the mode, object, and stage will be
omitted. If -z is passed, the "lines" are terminated by a NUL
character instead of a newline character.
Informational messages
This section provides informational messages, typically about
conflicts. The format of the section varies significantly
depending on whether -z is passed.
If -z is passed:
The output format is zero or more conflict informational records,
each of the form:
<list-of-paths><conflict-type>NUL<conflict-message>NUL
where <list-of-paths> is of the form
<number-of-paths>NUL<path1>NUL<path2>NUL...<pathN>NUL
and includes paths (or branch names) affected by the conflict or
informational message in <conflict-message>. Also, <conflict-type>
is a stable string explaining the type of conflict, such as
• "Auto-merging"
• "CONFLICT (rename/delete)"
• "CONFLICT (submodule lacks merge base)"
• "CONFLICT (binary)"
and <conflict-message> is a more detailed message about the
conflict which often (but not always) embeds the
<stable-short-type-description> within it. These strings may
change in future Git versions. Some examples:
• "Auto-merging <file>"
• "CONFLICT (rename/delete): <oldfile> renamed...but deleted
in..."
• "Failed to merge submodule <submodule> (no merge base)"
• "Warning: cannot merge binary files: <filename>"
If -z is NOT passed:
This section starts with a blank line to separate it from the
previous sections, and then only contains the <conflict-message>
information from the previous section (separated by newlines).
These are non-stable strings that should not be parsed by scripts,
and are just meant for human consumption. Also, note that while
<conflict-message> strings usually do not contain embedded
newlines, they sometimes do. (However, the free-form messages will
never have an embedded NUL character). So, the entire block of
information is meant for human readers as an agglomeration of all
conflict messages.
For a successful, non-conflicted merge, the exit status is 0. When
the merge has conflicts, the exit status is 1. If the merge is not
able to complete (or start) due to some kind of error, the exit
status is something other than 0 or 1 (and the output is
unspecified). When --stdin is passed, the return status is 0 for
both successful and conflicted merges, and something other than 0
or 1 if it cannot complete all the requested merges.
This command is intended as low-level plumbing, similar to
git-hash-object(1), git-mktree(1), git-commit-tree(1),
git-write-tree(1), git-update-ref(1), and git-mktag(1). Thus, it
can be used as a part of a series of steps such as:
vi message.txt
BRANCH1=refs/heads/test
BRANCH2=main
NEWTREE=$(git merge-tree --write-tree $BRANCH1 $BRANCH2) || {
echo "There were conflicts..." 1>&2
exit 1
}
NEWCOMMIT=$(git commit-tree $NEWTREE -F message.txt \
-p $BRANCH1 -p $BRANCH2)
git update-ref $BRANCH1 $NEWCOMMIT
Note that when the exit status is non-zero, NEWTREE in this
sequence will contain a lot more output than just a tree.
For conflicts, the output includes the same information that you’d
get with git-merge(1):
• what would be written to the working tree (the OID of toplevel
tree)
• the higher order stages that would be written to the index
(the Conflicted file info)
• any messages that would have been printed to stdout (the
Informational messages)
git merge-tree --stdin input format is fully text based. Each line
has this format:
[<base-commit> -- ]<branch1> <branch2>
If one line is separated by --, the string before the separator is
used for specifying a merge-base for the merge and the string
after the separator describes the branches to be merged.
Do NOT look through the resulting toplevel tree to try to find
which files conflict; parse the Conflicted file info section
instead. Not only would parsing an entire tree be horrendously
slow in large repositories, there are numerous types of conflicts
not representable by conflict markers (modify/delete, mode
conflict, binary file changed on both sides, file/directory
conflicts, various rename conflict permutations, etc.)
Do NOT interpret an empty Conflicted file info list as a clean
merge; check the exit status. A merge can have conflicts without
having individual files conflict (there are a few types of
directory rename conflicts that fall into this category, and
others might also be added in the future).
Do NOT attempt to guess or make the user guess the conflict types
from the Conflicted file info list. The information there is
insufficient to do so. For example: Rename/rename(1to2) conflicts
(both sides renamed the same file differently) will result in
three different files having higher order stages (but each only
has one higher order stage), with no way (short of the
Informational messages section) to determine which three files are
related. File/directory conflicts also result in a file with
exactly one higher order stage.
Possibly-involved-in-directory-rename conflicts (when
"merge.directoryRenames" is unset or set to "conflicts") also
result in a file with exactly one higher order stage. In all
cases, the Informational messages section has the necessary info,
though it is not designed to be machine parseable.
Do NOT assume that each path from Conflicted file info, and the
logical conflicts in the Informational messages have a one-to-one
mapping, nor that there is a one-to-many mapping, nor a
many-to-one mapping. Many-to-many mappings exist, meaning that
each path can have many logical conflict types in a single merge,
and each logical conflict type can affect many paths.
Do NOT assume all filenames listed in the Informational messages
section had conflicts. Messages can be included for files that
have no conflicts, such as "Auto-merging <file>".
AVOID taking the OIDS from the Conflicted file info and re-merging
them to present the conflicts to the user. This will lose
information. Instead, look up the version of the file found within
the OID of toplevel tree and show that instead. In particular, the
latter will have conflict markers annotated with the original
branch/commit being merged and, if renames were involved, the
original filename. While you could include the original
branch/commit in the conflict marker annotations when re-merging,
the original filename is not available from the Conflicted file
info and thus you would be losing information that might help the
user resolve the conflict.
Per the DESCRIPTION and unlike the rest of this documentation,
this section describes the deprecated --trivial-merge mode.
Other than the optional --trivial-merge, this mode accepts no
options.
This mode reads three tree-ish, and outputs trivial merge results
and conflicting stages to the standard output in a semi-diff
format. Since this was designed for higher level scripts to
consume and merge the results back into the index, it omits
entries that match <branch1>. The result of this second form is
similar to what three-way git read-tree -m does, but instead of
storing the results in the index, the command outputs the entries
to the standard output.
This form not only has limited applicability (a trivial merge
cannot handle content merges of individual files, rename
detection, proper directory/file conflict handling, etc.), the
output format is also difficult to work with, and it will
generally be less performant than the first form even on
successful merges (especially if working in large repositories).
Part of the git(1) suite
This page is part of the git (Git distributed version control
system) project. Information about the project can be found at
⟨http://git-scm.com/⟩. If you have a bug report for this manual
page, see ⟨http://git-scm.com/community⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/git/git.git⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-07.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Git 2.51.0.rc1 2025-08-07 GIT-MERGE-TREE(1)
Pages that refer to this page: git(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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