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4 <article lang="en" id="git-merge(1)">
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6 <title>git-merge(1)</title>
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8 <primary>git-merge(1)</primary>
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11 <simplesect id="_name">
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13 <simpara>git-merge - Join two or more development histories together</simpara>
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15 <simplesect id="_synopsis">
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16 <title>SYNOPSIS</title>
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18 <literallayout><emphasis>git merge</emphasis> [-n] [--stat] [--no-commit] [--squash] [-s <strategy>]…
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19 [-m <msg>] <remote> <remote>…
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20 <emphasis>git merge</emphasis> <msg> HEAD <remote>…</literallayout>
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23 <simplesect id="_description">
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24 <title>DESCRIPTION</title>
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25 <simpara>This is the top-level interface to the merge machinery
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26 which drives multiple merge strategy scripts.</simpara>
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27 <simpara>The second syntax (<msg> <literal>HEAD</literal> <remote>) is supported for
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28 historical reasons. Do not use it from the command line or in
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29 new scripts. It is the same as <literal>git merge -m <msg> <remote></literal>.</simpara>
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31 <simplesect id="_options">
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32 <title>OPTIONS</title>
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66 Show a diffstat at the end of the merge. The diffstat is also
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67 controlled by the configuration option merge.stat.
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80 Do not show a diffstat at the end of the merge.
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93 Synonyms to --stat and --no-stat; these are deprecated and will be
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94 removed in the future.
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104 In addition to branch names, populate the log message with
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105 one-line descriptions from the actual commits that are being
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116 Do not list one-line descriptions from the actual commits being
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127 Perform the merge but pretend the merge failed and do
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128 not autocommit, to give the user a chance to inspect and
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129 further tweak the merge result before committing.
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139 Perform the merge and commit the result. This option can
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140 be used to override --no-commit.
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150 Produce the working tree and index state as if a real
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151 merge happened, but do not actually make a commit or
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152 move the <literal>HEAD</literal>, nor record <literal>$GIT_DIR/MERGE_HEAD</literal> to
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153 cause the next <literal>git commit</literal> command to create a merge
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154 commit. This allows you to create a single commit on
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155 top of the current branch whose effect is the same as
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156 merging another branch (or more in case of an octopus).
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166 Perform the merge and commit the result. This option can
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167 be used to override --squash.
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177 Generate a merge commit even if the merge resolved as a
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188 Do not generate a merge commit if the merge resolved as
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189 a fast-forward, only update the branch pointer. This is
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190 the default behavior of git-merge.
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196 -s <strategy>
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199 --strategy=<strategy>
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203 Use the given merge strategy; can be supplied more than
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204 once to specify them in the order they should be tried.
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205 If there is no <literal>-s</literal> option, a built-in list of strategies
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206 is used instead (<emphasis>git-merge-recursive</emphasis> when merging a single
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207 head, <emphasis>git-merge-octopus</emphasis> otherwise).
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217 The commit message to be used for the merge commit (in case
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218 it is created). The <emphasis>git-fmt-merge-msg</emphasis> script can be used
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219 to give a good default for automated <emphasis>git-merge</emphasis> invocations.
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225 <remote>…
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229 Other branch heads to merge into our branch. You need at
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230 least one <remote>. Specifying more than one <remote>
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231 obviously means you are trying an Octopus.
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237 <simplesect id="_merge_strategies">
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238 <title>MERGE STRATEGIES</title>
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246 This can only resolve two heads (i.e. the current branch
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247 and another branch you pulled from) using 3-way merge
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248 algorithm. It tries to carefully detect criss-cross
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249 merge ambiguities and is considered generally safe and
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260 This can only resolve two heads using 3-way merge
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261 algorithm. When there are more than one common
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262 ancestors that can be used for 3-way merge, it creates a
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263 merged tree of the common ancestors and uses that as
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264 the reference tree for the 3-way merge. This has been
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265 reported to result in fewer merge conflicts without
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266 causing mis-merges by tests done on actual merge commits
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267 taken from Linux 2.6 kernel development history.
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268 Additionally this can detect and handle merges involving
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269 renames. This is the default merge strategy when
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270 pulling or merging one branch.
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280 This resolves more than two-head case, but refuses to do
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281 complex merge that needs manual resolution. It is
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282 primarily meant to be used for bundling topic branch
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283 heads together. This is the default merge strategy when
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284 pulling or merging more than one branches.
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294 This resolves any number of heads, but the result of the
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295 merge is always the current branch head. It is meant to
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296 be used to supersede old development history of side
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307 This is a modified recursive strategy. When merging trees A and
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308 B, if B corresponds to a subtree of A, B is first adjusted to
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309 match the tree structure of A, instead of reading the trees at
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310 the same level. This adjustment is also done to the common
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316 <simpara>If you tried a merge which resulted in a complex conflicts and
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317 would want to start over, you can recover with <emphasis>git-reset</emphasis>.</simpara>
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319 <simplesect id="_configuration">
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320 <title>CONFIGURATION</title>
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324 merge.conflictstyle
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328 Specify the style in which conflicted hunks are written out to
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329 working tree files upon merge. The default is "merge", which
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330 shows a <literal><<<<<<<</literal> conflict marker, changes made by one side,
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331 a <literal>=======</literal> marker, changes made by the other side, and then
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332 a <literal>>>>>>>></literal> marker. An alternate style, "diff3", adds a <literal>|||||||</literal>
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333 marker and the original text before the <literal>=======</literal> marker.
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343 Whether to include summaries of merged commits in newly created
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344 merge commit messages. False by default.
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354 The number of files to consider when performing rename detection
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355 during a merge; if not specified, defaults to the value of
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366 Whether to print the diffstat between ORIG_HEAD and the merge result
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367 at the end of the merge. True by default.
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377 Controls which merge resolution program is used by
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378 <xref linkend="git-mergetool(1)"/>. Valid built-in values are: "kdiff3",
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379 "tkdiff", "meld", "xxdiff", "emerge", "vimdiff", "gvimdiff", and
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380 "opendiff". Any other value is treated is custom merge tool
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381 and there must be a corresponding mergetool.<tool>.cmd option.
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391 Controls the amount of output shown by the recursive merge
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392 strategy. Level 0 outputs nothing except a final error
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393 message if conflicts were detected. Level 1 outputs only
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394 conflicts, 2 outputs conflicts and file changes. Level 5 and
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395 above outputs debugging information. The default is level 2.
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396 Can be overridden by the <emphasis>GIT_MERGE_VERBOSITY</emphasis> environment variable.
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402 merge.<driver>.name
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406 Defines a human-readable name for a custom low-level
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407 merge driver. See <xref linkend="gitattributes(5)"/> for details.
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413 merge.<driver>.driver
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417 Defines the command that implements a custom low-level
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418 merge driver. See <xref linkend="gitattributes(5)"/> for details.
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424 merge.<driver>.recursive
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428 Names a low-level merge driver to be used when
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429 performing an internal merge between common ancestors.
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430 See <xref linkend="gitattributes(5)"/> for details.
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436 branch.<name>.mergeoptions
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440 Sets default options for merging into branch <name>. The syntax and
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441 supported options are equal to that of <emphasis>git-merge</emphasis>, but option values
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442 containing whitespace characters are currently not supported.
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448 <simplesect id="_how_merge_works">
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449 <title>HOW MERGE WORKS</title>
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450 <simpara>A merge is always between the current <literal>HEAD</literal> and one or more
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451 commits (usually, branch head or tag), and the index file must
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452 match the tree of <literal>HEAD</literal> commit (i.e. the contents of the last commit)
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453 when it starts out. In other words, <literal>git diff --cached HEAD</literal> must
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454 report no changes. (One exception is when the changed index
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455 entries are already in the same state that would result from
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456 the merge anyway.)</simpara>
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457 <simpara>Three kinds of merge can happen:</simpara>
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461 The merged commit is already contained in <literal>HEAD</literal>. This is the
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462 simplest case, called "Already up-to-date."
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467 <literal>HEAD</literal> is already contained in the merged commit. This is the
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468 most common case especially when invoked from <emphasis>git pull</emphasis>:
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469 you are tracking an upstream repository, have committed no local
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470 changes and now you want to update to a newer upstream revision.
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471 Your <literal>HEAD</literal> (and the index) is updated to point at the merged
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472 commit, without creating an extra merge commit. This is
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473 called "Fast-forward".
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478 Both the merged commit and <literal>HEAD</literal> are independent and must be
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479 tied together by a merge commit that has both of them as its parents.
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480 The rest of this section describes this "True merge" case.
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484 <simpara>The chosen merge strategy merges the two commits into a single
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486 When things merge cleanly, this is what happens:</simpara>
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487 <orderedlist numeration="arabic">
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490 The results are updated both in the index file and in your
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496 Index file is written out as a tree;
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501 The tree gets committed; and
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506 The <literal>HEAD</literal> pointer gets advanced.
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510 <simpara>Because of 2., we require that the original state of the index
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511 file matches exactly the current <literal>HEAD</literal> commit; otherwise we
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512 will write out your local changes already registered in your
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513 index file along with the merge result, which is not good.
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514 Because 1. involves only those paths differing between your
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515 branch and the remote branch you are pulling from during the
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516 merge (which is typically a fraction of the whole tree), you can
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517 have local modifications in your working tree as long as they do
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518 not overlap with what the merge updates.</simpara>
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519 <simpara>When there are conflicts, the following happens:</simpara>
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520 <orderedlist numeration="arabic">
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523 <literal>HEAD</literal> stays the same.
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528 Cleanly merged paths are updated both in the index file and
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529 in your working tree.
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534 For conflicting paths, the index file records up to three
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535 versions; stage1 stores the version from the common ancestor,
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536 stage2 from <literal>HEAD</literal>, and stage3 from the remote branch (you
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537 can inspect the stages with <literal>git ls-files -u</literal>). The working
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538 tree files contain the result of the "merge" program; i.e. 3-way
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539 merge results with familiar conflict markers <literal><<< === >>></literal>.
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544 No other changes are done. In particular, the local
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545 modifications you had before you started merge will stay the
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546 same and the index entries for them stay as they were,
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547 i.e. matching <literal>HEAD</literal>.
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552 <simplesect id="_how_conflicts_are_presented">
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553 <title>HOW CONFLICTS ARE PRESENTED</title>
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554 <simpara>During a merge, the working tree files are updated to reflect the result
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555 of the merge. Among the changes made to the common ancestor’s version,
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556 non-overlapping ones (that is, you changed an area of the file while the
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557 other side left that area intact, or vice versa) are incorporated in the
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558 final result verbatim. When both sides made changes to the same area,
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559 however, git cannot randomly pick one side over the other, and asks you to
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560 resolve it by leaving what both sides did to that area.</simpara>
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561 <simpara>By default, git uses the same style as that is used by "merge" program
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562 from the RCS suite to present such a conflicted hunk, like this:</simpara>
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563 <literallayout>Here are lines that are either unchanged from the common
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564 ancestor, or cleanly resolved because only one side changed.
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565 <<<<<<< yours:sample.txt
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566 Conflict resolution is hard;
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569 Git makes conflict resolution easy.
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570 >>>>>>> theirs:sample.txt
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571 And here is another line that is cleanly resolved or unmodified.</literallayout>
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572 <simpara>The area where a pair of conflicting changes happened is marked with markers
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573 "<literal><<<<<<<</literal>", "<literal>=======</literal>", and "<literal>>>>>>>></literal>". The part before the "<literal>=======</literal>"
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574 is typically your side, and the part afterwards is typically their side.</simpara>
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575 <simpara>The default format does not show what the original said in the conflicting
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576 area. You cannot tell how many lines are deleted and replaced with
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577 Barbie’s remark on your side. The only thing you can tell is that your
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578 side wants to say it is hard and you’d prefer to go shopping, while the
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579 other side wants to claim it is easy.</simpara>
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580 <simpara>An alternative style can be used by setting the "merge.conflictstyle"
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581 configuration variable to "diff3". In "diff3" style, the above conflict
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582 may look like this:</simpara>
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583 <literallayout>Here are lines that are either unchanged from the common
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584 ancestor, or cleanly resolved because only one side changed.
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585 <<<<<<< yours:sample.txt
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586 Conflict resolution is hard;
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589 Conflict resolution is hard.
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591 Git makes conflict resolution easy.
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592 >>>>>>> theirs:sample.txt
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593 And here is another line that is cleanly resolved or unmodified.</literallayout>
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594 <simpara>In addition to the "<literal><<<<<<<</literal>", "<literal>=======</literal>", and "<literal>>>>>>>></literal>" markers, it uses
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595 another "<literal>|||||||</literal>" marker that is followed by the original text. You can
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596 tell that the original just stated a fact, and your side simply gave in to
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597 that statement and gave up, while the other side tried to have a more
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598 positive attitude. You can sometimes come up with a better resolution by
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599 viewing the original.</simpara>
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601 <simplesect id="_how_to_resolve_conflicts">
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602 <title>HOW TO RESOLVE CONFLICTS</title>
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603 <simpara>After seeing a conflict, you can do two things:</simpara>
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607 Decide not to merge. The only clean-ups you need are to reset
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608 the index file to the <literal>HEAD</literal> commit to reverse 2. and to clean
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609 up working tree changes made by 2. and 3.; <emphasis>git-reset --hard</emphasis> can
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615 Resolve the conflicts. Git will mark the conflicts in
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616 the working tree. Edit the files into shape and
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617 <emphasis>git-add</emphasis> them to the index. Use <emphasis>git-commit</emphasis> to seal the deal.
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621 <simpara>You can work through the conflict with a number of tools:</simpara>
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625 Use a mergetool. <emphasis>git mergetool</emphasis> to launch a graphical
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626 mergetool which will work you through the merge.
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631 Look at the diffs. <emphasis>git diff</emphasis> will show a three-way diff,
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632 highlighting changes from both the HEAD and remote versions.
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637 Look at the diffs on their own. <emphasis>git log --merge -p <path></emphasis>
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638 will show diffs first for the HEAD version and then the
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644 Look at the originals. <emphasis>git show :1:filename</emphasis> shows the
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645 common ancestor, <emphasis>git show :2:filename</emphasis> shows the HEAD
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646 version and <emphasis>git show :3:filename</emphasis> shows the remote version.
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651 <simplesect id="_see_also">
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652 <title>SEE ALSO</title>
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653 <simpara><xref linkend="git-fmt-merge-msg(1)"/>, <xref linkend="git-pull(1)"/>,
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654 <xref linkend="gitattributes(5)"/>,
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655 <xref linkend="git-reset(1)"/>,
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656 <xref linkend="git-diff(1)"/>, <xref linkend="git-ls-files(1)"/>,
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657 <xref linkend="git-add(1)"/>, <xref linkend="git-rm(1)"/>,
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658 <xref linkend="git-mergetool(1)"/></simpara>
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660 <simplesect id="_author">
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661 <title>Author</title>
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662 <simpara>Written by Junio C Hamano <<ulink url="mailto:gitster@pobox.com">gitster@pobox.com</ulink>></simpara>
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664 <simplesect id="_documentation">
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665 <title>Documentation</title>
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666 <simpara>Documentation by Junio C Hamano and the git-list <<ulink url="mailto:git@vger.kernel.org">git@vger.kernel.org</ulink>>.</simpara>
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668 <simplesect id="_git">
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670 <simpara>Part of the <xref linkend="git(1)"/> suite</simpara>
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