oracular (1) git-merge-tree.1.gz

NAME

       git-merge-tree - Perform merge without touching index or working tree

SYNOPSIS

       git merge-tree [--write-tree] [<options>] <branch1> <branch2>
       git merge-tree [--trivial-merge] <base-tree> <branch1> <branch2> (deprecated)

DESCRIPTION

       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.

OPTIONS

       -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           Do not quote filenames in the 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 the section called “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.

       --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.

OUTPUT

       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
           <0: something prevented the merge from running (e.g. access to repository
               objects denied by filesystem)

   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.

EXIT STATUS

       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.

USAGE NOTES

       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:

           NEWTREE=$(git merge-tree --write-tree $BRANCH1 $BRANCH2)
           test $? -eq 0 || die "There were conflicts..."
           NEWCOMMIT=$(git commit-tree $NEWTREE -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)

INPUT FORMAT

       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.

MISTAKES TO AVOID

       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.

DEPRECATED DESCRIPTION

       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).

GIT

       Part of the git(1) suite