Documentation/git-merge-tree.txt

   1 git-merge-tree(1)
   2 =================
   3
   4 NAME
   5 ----
   6 git-merge-tree - Perform merge without touching index or working tree
   7
   8
   9 SYNOPSIS
  10 --------
  11 [verse]
  12 'git merge-tree' [--write-tree] [<options>] <branch1> <branch2>
  13 'git merge-tree' [--trivial-merge] <base-tree> <branch1> <branch2> (deprecated)
  14
  15 [[NEWMERGE]]
  16 DESCRIPTION
  17 -----------
  18
  19 This command has a modern `--write-tree` mode and a deprecated
  20 `--trivial-merge` mode.  With the exception of the
  21 <<DEPMERGE,DEPRECATED DESCRIPTION>> section at the end, the rest of
  22 this documentation describes the modern `--write-tree` mode.
  23
  24 Performs a merge, but does not make any new commits and does not read
  25 from or write to either the working tree or index.
  26
  27 The performed merge will use the same features as the "real"
  28 linkgit:git-merge[1], including:
  29
  30   * three way content merges of individual files
  31   * rename detection
  32   * proper directory/file conflict handling
  33   * recursive ancestor consolidation (i.e. when there is more than one
  34     merge base, creating a virtual merge base by merging the merge bases)
  35   * etc.
  36
  37 After the merge completes, a new toplevel tree object is created.  See
  38 `OUTPUT` below for details.
  39
  40 OPTIONS
  41 -------
  42
  43 -z::
  44         Do not quote filenames in the <Conflicted file info> section,
  45         and end each filename with a NUL character rather than
  46         newline.  Also begin the messages section with a NUL character
  47         instead of a newline.  See <<OUTPUT>> below for more information.
  48
  49 --name-only::
  50         In the Conflicted file info section, instead of writing a list
  51         of (mode, oid, stage, path) tuples to output for conflicted
  52         files, just provide a list of filenames with conflicts (and
  53         do not list filenames multiple times if they have multiple
  54         conflicting stages).
  55
  56 --[no-]messages::
  57         Write any informational messages such as "Auto-merging <path>"
  58         or CONFLICT notices to the end of stdout.  If unspecified, the
  59         default is to include these messages if there are merge
  60         conflicts, and to omit them otherwise.
  61
  62 --allow-unrelated-histories::
  63         merge-tree will by default error out if the two branches specified
  64         share no common history.  This flag can be given to override that
  65         check and make the merge proceed anyway.
  66
  67 --merge-base=<commit>::
  68         Instead of finding the merge-bases for <branch1> and <branch2>,
  69         specify a merge-base for the merge, and specifying multiple bases is
  70         currently not supported. This option is incompatible with `--stdin`.
  71
  72 [[OUTPUT]]
  73 OUTPUT
  74 ------
  75
  76 For a successful merge, the output from git-merge-tree is simply one
  77 line:
  78
  79         <OID of toplevel tree>
  80
  81 Whereas for a conflicted merge, the output is by default of the form:
  82
  83         <OID of toplevel tree>
  84         <Conflicted file info>
  85         <Informational messages>
  86
  87 These are discussed individually below.
  88
  89 However, there is an exception.  If `--stdin` is passed, then there is
  90 an extra section at the beginning, a NUL character at the end, and then
  91 all the sections repeat for each line of input.  Thus, if the first merge
  92 is conflicted and the second is clean, the output would be of the form:
  93
  94         <Merge status>
  95         <OID of toplevel tree>
  96         <Conflicted file info>
  97         <Informational messages>
  98         NUL
  99         <Merge status>
 100         <OID of toplevel tree>
 101         NUL
 102
 103 [[MS]]
 104 Merge status
 105 ~~~~~~~~~~~~
 106
 107 This is an integer status followed by a NUL character.  The integer status is:
 108
 109      0: merge had conflicts
 110      1: merge was clean
 111      <0: something prevented the merge from running (e.g. access to repository
 112          objects denied by filesystem)
 113
 114 [[OIDTLT]]
 115 OID of toplevel tree
 116 ~~~~~~~~~~~~~~~~~~~~
 117
 118 This is a tree object that represents what would be checked out in the
 119 working tree at the end of `git merge`.  If there were conflicts, then
 120 files within this tree may have embedded conflict markers.  This section
 121 is always followed by a newline (or NUL if `-z` is passed).
 122
 123 [[CFI]]
 124 Conflicted file info
 125 ~~~~~~~~~~~~~~~~~~~~
 126
 127 This is a sequence of lines with the format
 128
 129         <mode> <object> <stage> <filename>
 130
 131 The filename will be quoted as explained for the configuration
 132 variable `core.quotePath` (see linkgit:git-config[1]).  However, if
 133 the `--name-only` option is passed, the mode, object, and stage will
 134 be omitted.  If `-z` is passed, the "lines" are terminated by a NUL
 135 character instead of a newline character.
 136
 137 [[IM]]
 138 Informational messages
 139 ~~~~~~~~~~~~~~~~~~~~~~
 140
 141 This section provides informational messages, typically about
 142 conflicts.  The format of the section varies significantly depending
 143 on whether `-z` is passed.
 144
 145 If `-z` is passed:
 146
 147 The output format is zero or more conflict informational records, each
 148 of the form:
 149
 150         <list-of-paths><conflict-type>NUL<conflict-message>NUL
 151
 152 where <list-of-paths> is of the form
 153
 154         <number-of-paths>NUL<path1>NUL<path2>NUL...<pathN>NUL
 155
 156 and includes paths (or branch names) affected by the conflict or
 157 informational message in <conflict-message>.  Also, <conflict-type> is a
 158 stable string explaining the type of conflict, such as
 159
 160   * "Auto-merging"
 161   * "CONFLICT (rename/delete)"
 162   * "CONFLICT (submodule lacks merge base)"
 163   * "CONFLICT (binary)"
 164
 165 and <conflict-message> is a more detailed message about the conflict which often
 166 (but not always) embeds the <stable-short-type-description> within it.  These
 167 strings may change in future Git versions.  Some examples:
 168
 169   * "Auto-merging <file>"
 170   * "CONFLICT (rename/delete): <oldfile> renamed...but deleted in..."
 171   * "Failed to merge submodule <submodule> (no merge base)"
 172   * "Warning: cannot merge binary files: <filename>"
 173
 174 If `-z` is NOT passed:
 175
 176 This section starts with a blank line to separate it from the previous
 177 sections, and then only contains the <conflict-message> information
 178 from the previous section (separated by newlines).  These are
 179 non-stable strings that should not be parsed by scripts, and are just
 180 meant for human consumption.  Also, note that while <conflict-message>
 181 strings usually do not contain embedded newlines, they sometimes do.
 182 (However, the free-form messages will never have an embedded NUL
 183 character).  So, the entire block of information is meant for human
 184 readers as an agglomeration of all conflict messages.
 185
 186 EXIT STATUS
 187 -----------
 188
 189 For a successful, non-conflicted merge, the exit status is 0.  When the
 190 merge has conflicts, the exit status is 1.  If the merge is not able to
 191 complete (or start) due to some kind of error, the exit status is
 192 something other than 0 or 1 (and the output is unspecified).  When
 193 --stdin is passed, the return status is 0 for both successful and
 194 conflicted merges, and something other than 0 or 1 if it cannot complete
 195 all the requested merges.
 196
 197 USAGE NOTES
 198 -----------
 199
 200 This command is intended as low-level plumbing, similar to
 201 linkgit:git-hash-object[1], linkgit:git-mktree[1],
 202 linkgit:git-commit-tree[1], linkgit:git-write-tree[1],
 203 linkgit:git-update-ref[1], and linkgit:git-mktag[1].  Thus, it can be
 204 used as a part of a series of steps such as:
 205
 206        NEWTREE=$(git merge-tree --write-tree $BRANCH1 $BRANCH2)
 207        test $? -eq 0 || die "There were conflicts..."
 208        NEWCOMMIT=$(git commit-tree $NEWTREE -p $BRANCH1 -p $BRANCH2)
 209        git update-ref $BRANCH1 $NEWCOMMIT
 210
 211 Note that when the exit status is non-zero, `NEWTREE` in this sequence
 212 will contain a lot more output than just a tree.
 213
 214 For conflicts, the output includes the same information that you'd get
 215 with linkgit:git-merge[1]:
 216
 217   * what would be written to the working tree (the
 218     <<OIDTLT,OID of toplevel tree>>)
 219   * the higher order stages that would be written to the index (the
 220     <<CFI,Conflicted file info>>)
 221   * any messages that would have been printed to stdout (the
 222     <<IM,Informational messages>>)
 223
 224 INPUT FORMAT
 225 ------------
 226 'git merge-tree --stdin' input format is fully text based. Each line
 227 has this format:
 228
 229         [<base-commit> -- ]<branch1> <branch2>
 230
 231 If one line is separated by `--`, the string before the separator is
 232 used for specifying a merge-base for the merge and the string after
 233 the separator describes the branches to be merged.
 234
 235 MISTAKES TO AVOID
 236 -----------------
 237
 238 Do NOT look through the resulting toplevel tree to try to find which
 239 files conflict; parse the <<CFI,Conflicted file info>> section instead.
 240 Not only would parsing an entire tree be horrendously slow in large
 241 repositories, there are numerous types of conflicts not representable by
 242 conflict markers (modify/delete, mode conflict, binary file changed on
 243 both sides, file/directory conflicts, various rename conflict
 244 permutations, etc.)
 245
 246 Do NOT interpret an empty <<CFI,Conflicted file info>> list as a clean
 247 merge; check the exit status.  A merge can have conflicts without having
 248 individual files conflict (there are a few types of directory rename
 249 conflicts that fall into this category, and others might also be added
 250 in the future).
 251
 252 Do NOT attempt to guess or make the user guess the conflict types from
 253 the <<CFI,Conflicted file info>> list.  The information there is
 254 insufficient to do so.  For example: Rename/rename(1to2) conflicts (both
 255 sides renamed the same file differently) will result in three different
 256 files having higher order stages (but each only has one higher order
 257 stage), with no way (short of the <<IM,Informational messages>> section)
 258 to determine which three files are related.  File/directory conflicts
 259 also result in a file with exactly one higher order stage.
 260 Possibly-involved-in-directory-rename conflicts (when
 261 "merge.directoryRenames" is unset or set to "conflicts") also result in
 262 a file with exactly one higher order stage.  In all cases, the
 263 <<IM,Informational messages>> section has the necessary info, though it
 264 is not designed to be machine parseable.
 265
 266 Do NOT assume that each path from <<CFI,Conflicted file info>>, and
 267 the logical conflicts in the <<IM,Informational messages>> have a
 268 one-to-one mapping, nor that there is a one-to-many mapping, nor a
 269 many-to-one mapping.  Many-to-many mappings exist, meaning that each
 270 path can have many logical conflict types in a single merge, and each
 271 logical conflict type can affect many paths.
 272
 273 Do NOT assume all filenames listed in the <<IM,Informational messages>>
 274 section had conflicts.  Messages can be included for files that have no
 275 conflicts, such as "Auto-merging <file>".
 276
 277 AVOID taking the OIDS from the <<CFI,Conflicted file info>> and
 278 re-merging them to present the conflicts to the user.  This will lose
 279 information.  Instead, look up the version of the file found within the
 280 <<OIDTLT,OID of toplevel tree>> and show that instead.  In particular,
 281 the latter will have conflict markers annotated with the original
 282 branch/commit being merged and, if renames were involved, the original
 283 filename.  While you could include the original branch/commit in the
 284 conflict marker annotations when re-merging, the original filename is
 285 not available from the <<CFI,Conflicted file info>> and thus you would
 286 be losing information that might help the user resolve the conflict.
 287
 288 [[DEPMERGE]]
 289 DEPRECATED DESCRIPTION
 290 ----------------------
 291
 292 Per the <<NEWMERGE,DESCRIPTION>> and unlike the rest of this
 293 documentation, this section describes the deprecated `--trivial-merge`
 294 mode.
 295
 296 Other than the optional `--trivial-merge`, this mode accepts no
 297 options.
 298
 299 This mode reads three tree-ish, and outputs trivial merge results and
 300 conflicting stages to the standard output in a semi-diff format.
 301 Since this was designed for higher level scripts to consume and merge
 302 the results back into the index, it omits entries that match
 303 <branch1>.  The result of this second form is similar to what
 304 three-way 'git read-tree -m' does, but instead of storing the results
 305 in the index, the command outputs the entries to the standard output.
 306
 307 This form not only has limited applicability (a trivial merge cannot
 308 handle content merges of individual files, rename detection, proper
 309 directory/file conflict handling, etc.), the output format is also
 310 difficult to work with, and it will generally be less performant than
 311 the first form even on successful merges (especially if working in
 312 large repositories).
 313
 314 GIT
 315 ---
 316 Part of the linkgit:git[1] suite