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300 lines
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300 lines
10 KiB
git-merge(1) |
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============ |
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NAME |
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---- |
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git-merge - Join two or more development histories together |
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SYNOPSIS |
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-------- |
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[verse] |
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'git merge' [-n] [--stat] [--no-commit] [--squash] |
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[-s <strategy>] [-X <strategy-option>] |
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[--[no-]rerere-autoupdate] [-m <msg>] <commit>... |
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'git merge' <msg> HEAD <commit>... |
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DESCRIPTION |
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----------- |
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Incorporates changes from the named commits (since the time their |
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histories diverged from the current branch) into the current |
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branch. This command is used by 'git pull' to incorporate changes |
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from another repository and can be used by hand to merge changes |
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from one branch into another. |
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Assume the following history exists and the current branch is |
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"`master`": |
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------------ |
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A---B---C topic |
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/ |
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D---E---F---G master |
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------------ |
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Then "`git merge topic`" will replay the changes made on the |
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`topic` branch since it diverged from `master` (i.e., `E`) until |
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its current commit (`C`) on top of `master`, and record the result |
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in a new commit along with the names of the two parent commits and |
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a log message from the user describing the changes. |
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------------ |
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A---B---C topic |
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/ \ |
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D---E---F---G---H master |
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------------ |
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The second syntax (<msg> `HEAD` <commit>...) is supported for |
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historical reasons. Do not use it from the command line or in |
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new scripts. It is the same as `git merge -m <msg> <commit>...`. |
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*Warning*: Running 'git merge' with uncommitted changes is |
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discouraged: while possible, it leaves you in a state that is hard to |
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back out of in the case of a conflict. |
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OPTIONS |
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------- |
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include::merge-options.txt[] |
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-m <msg>:: |
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Set the commit message to be used for the merge commit (in |
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case one is created). The 'git fmt-merge-msg' command can be |
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used to give a good default for automated 'git merge' |
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invocations. |
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--rerere-autoupdate:: |
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--no-rerere-autoupdate:: |
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Allow the rerere mechanism to update the index with the |
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result of auto-conflict resolution if possible. |
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<commit>...:: |
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Commits, usually other branch heads, to merge into our branch. |
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You need at least one <commit>. Specifying more than one |
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<commit> obviously means you are trying an Octopus. |
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PRE-MERGE CHECKS |
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---------------- |
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Before applying outside changes, you should get your own work in |
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good shape and committed locally, so it will not be clobbered if |
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there are conflicts. See also linkgit:git-stash[1]. |
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'git pull' and 'git merge' will stop without doing anything when |
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local uncommitted changes overlap with files that 'git pull'/'git |
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merge' may need to update. |
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To avoid recording unrelated changes in the merge commit, |
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'git pull' and 'git merge' will also abort if there are any changes |
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registered in the index relative to the `HEAD` commit. (One |
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exception is when the changed index entries are in the state that |
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would result from the merge already.) |
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If all named commits are already ancestors of `HEAD`, 'git merge' |
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will exit early with the message "Already up-to-date." |
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FAST-FORWARD MERGE |
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------------------ |
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Often the current branch head is an ancestor of the named commit. |
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This is the most common case especially when invoked from 'git |
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pull': you are tracking an upstream repository, you have committed |
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no local changes, and now you want to update to a newer upstream |
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revision. In this case, a new commit is not needed to store the |
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combined history; instead, the `HEAD` (along with the index) is |
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updated to point at the named commit, without creating an extra |
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merge commit. |
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This behavior can be suppressed with the `--no-ff` option. |
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TRUE MERGE |
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---------- |
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Except in a fast-forward merge (see above), the branches to be |
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merged must be tied together by a merge commit that has both of them |
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as its parents. |
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A merged version reconciling the changes from all branches to be |
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merged is committed, and your `HEAD`, index, and working tree are |
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updated to it. It is possible to have modifications in the working |
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tree as long as they do not overlap; the update will preserve them. |
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When it is not obvious how to reconcile the changes, the following |
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happens: |
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1. The `HEAD` pointer stays the same. |
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2. The `MERGE_HEAD` ref is set to point to the other branch head. |
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3. Paths that merged cleanly are updated both in the index file and |
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in your working tree. |
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4. For conflicting paths, the index file records up to three |
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versions: stage 1 stores the version from the common ancestor, |
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stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you |
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can inspect the stages with `git ls-files -u`). The working |
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tree files contain the result of the "merge" program; i.e. 3-way |
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merge results with familiar conflict markers `<<<` `===` `>>>`. |
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5. No other changes are made. In particular, the local |
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modifications you had before you started merge will stay the |
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same and the index entries for them stay as they were, |
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i.e. matching `HEAD`. |
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If you tried a merge which resulted in complex conflicts and |
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want to start over, you can recover with `git reset --merge`. |
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HOW CONFLICTS ARE PRESENTED |
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--------------------------- |
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During a merge, the working tree files are updated to reflect the result |
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of the merge. Among the changes made to the common ancestor's version, |
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non-overlapping ones (that is, you changed an area of the file while the |
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other side left that area intact, or vice versa) are incorporated in the |
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final result verbatim. When both sides made changes to the same area, |
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however, git cannot randomly pick one side over the other, and asks you to |
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resolve it by leaving what both sides did to that area. |
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By default, git uses the same style as that is used by "merge" program |
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from the RCS suite to present such a conflicted hunk, like this: |
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------------ |
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Here are lines that are either unchanged from the common |
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ancestor, or cleanly resolved because only one side changed. |
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<<<<<<< yours:sample.txt |
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Conflict resolution is hard; |
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let's go shopping. |
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======= |
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Git makes conflict resolution easy. |
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>>>>>>> theirs:sample.txt |
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And here is another line that is cleanly resolved or unmodified. |
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------------ |
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The area where a pair of conflicting changes happened is marked with markers |
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`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======` |
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is typically your side, and the part afterwards is typically their side. |
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The default format does not show what the original said in the conflicting |
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area. You cannot tell how many lines are deleted and replaced with |
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Barbie's remark on your side. The only thing you can tell is that your |
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side wants to say it is hard and you'd prefer to go shopping, while the |
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other side wants to claim it is easy. |
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An alternative style can be used by setting the "merge.conflictstyle" |
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configuration variable to "diff3". In "diff3" style, the above conflict |
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may look like this: |
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------------ |
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Here are lines that are either unchanged from the common |
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ancestor, or cleanly resolved because only one side changed. |
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<<<<<<< yours:sample.txt |
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Conflict resolution is hard; |
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let's go shopping. |
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||||||| |
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Conflict resolution is hard. |
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======= |
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Git makes conflict resolution easy. |
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>>>>>>> theirs:sample.txt |
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And here is another line that is cleanly resolved or unmodified. |
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------------ |
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In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses |
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another `|||||||` marker that is followed by the original text. You can |
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tell that the original just stated a fact, and your side simply gave in to |
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that statement and gave up, while the other side tried to have a more |
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positive attitude. You can sometimes come up with a better resolution by |
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viewing the original. |
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HOW TO RESOLVE CONFLICTS |
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------------------------ |
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After seeing a conflict, you can do two things: |
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* Decide not to merge. The only clean-ups you need are to reset |
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the index file to the `HEAD` commit to reverse 2. and to clean |
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up working tree changes made by 2. and 3.; `git-reset --hard` can |
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be used for this. |
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* Resolve the conflicts. Git will mark the conflicts in |
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the working tree. Edit the files into shape and |
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'git add' them to the index. Use 'git commit' to seal the deal. |
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You can work through the conflict with a number of tools: |
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* Use a mergetool. `git mergetool` to launch a graphical |
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mergetool which will work you through the merge. |
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* Look at the diffs. `git diff` will show a three-way diff, |
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highlighting changes from both the `HEAD` and `MERGE_HEAD` |
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versions. |
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* Look at the diffs from each branch. `git log --merge -p <path>` |
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will show diffs first for the `HEAD` version and then the |
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`MERGE_HEAD` version. |
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* Look at the originals. `git show :1:filename` shows the |
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common ancestor, `git show :2:filename` shows the `HEAD` |
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version, and `git show :3:filename` shows the `MERGE_HEAD` |
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version. |
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EXAMPLES |
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-------- |
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* Merge branches `fixes` and `enhancements` on top of |
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the current branch, making an octopus merge: |
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+ |
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------------------------------------------------ |
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$ git merge fixes enhancements |
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------------------------------------------------ |
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* Merge branch `obsolete` into the current branch, using `ours` |
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merge strategy: |
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+ |
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------------------------------------------------ |
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$ git merge -s ours obsolete |
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------------------------------------------------ |
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* Merge branch `maint` into the current branch, but do not make |
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a new commit automatically: |
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+ |
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------------------------------------------------ |
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$ git merge --no-commit maint |
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------------------------------------------------ |
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+ |
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This can be used when you want to include further changes to the |
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merge, or want to write your own merge commit message. |
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+ |
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You should refrain from abusing this option to sneak substantial |
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changes into a merge commit. Small fixups like bumping |
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release/version name would be acceptable. |
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include::merge-strategies.txt[] |
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CONFIGURATION |
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------------- |
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include::merge-config.txt[] |
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branch.<name>.mergeoptions:: |
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Sets default options for merging into branch <name>. The syntax and |
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supported options are the same as those of 'git merge', but option |
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values containing whitespace characters are currently not supported. |
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SEE ALSO |
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-------- |
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linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1], |
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linkgit:gitattributes[5], |
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linkgit:git-reset[1], |
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linkgit:git-diff[1], linkgit:git-ls-files[1], |
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linkgit:git-add[1], linkgit:git-rm[1], |
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linkgit:git-mergetool[1] |
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Author |
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------ |
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Written by Junio C Hamano <gitster@pobox.com> |
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Documentation |
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-------------- |
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Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. |
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GIT |
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--- |
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Part of the linkgit:git[1] suite
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