136 lines
5.6 KiB
Text
136 lines
5.6 KiB
Text
MERGE STRATEGIES
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----------------
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The merge mechanism (`git merge` and `git pull` commands) allows the
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backend 'merge strategies' to be chosen with `-s` option. Some strategies
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can also take their own options, which can be passed by giving `-X<option>`
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arguments to `git merge` and/or `git pull`.
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resolve::
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This can only resolve two heads (i.e. the current branch
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and another branch you pulled from) using a 3-way merge
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algorithm. It tries to carefully detect criss-cross
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merge ambiguities and is considered generally safe and
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fast.
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recursive::
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This can only resolve two heads using a 3-way merge
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algorithm. When there is more than one common
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ancestor that can be used for 3-way merge, it creates a
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merged tree of the common ancestors and uses that as
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the reference tree for the 3-way merge. This has been
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reported to result in fewer merge conflicts without
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causing mismerges by tests done on actual merge commits
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taken from Linux 2.6 kernel development history.
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Additionally this can detect and handle merges involving
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renames, but currently cannot make use of detected
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copies. This is the default merge strategy when pulling
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or merging one branch.
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+
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The 'recursive' strategy can take the following options:
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ours;;
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This option forces conflicting hunks to be auto-resolved cleanly by
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favoring 'our' version. Changes from the other tree that do not
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conflict with our side are reflected to the merge result.
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For a binary file, the entire contents are taken from our side.
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+
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This should not be confused with the 'ours' merge strategy, which does not
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even look at what the other tree contains at all. It discards everything
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the other tree did, declaring 'our' history contains all that happened in it.
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theirs;;
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This is the opposite of 'ours'; note that, unlike 'ours', there is
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no 'theirs' merge strategy to confuse this merge option with.
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patience;;
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With this option, 'merge-recursive' spends a little extra time
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to avoid mismerges that sometimes occur due to unimportant
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matching lines (e.g., braces from distinct functions). Use
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this when the branches to be merged have diverged wildly.
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See also linkgit:git-diff[1] `--patience`.
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diff-algorithm=[patience|minimal|histogram|myers];;
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Tells 'merge-recursive' to use a different diff algorithm, which
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can help avoid mismerges that occur due to unimportant matching
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lines (such as braces from distinct functions). See also
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linkgit:git-diff[1] `--diff-algorithm`.
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ignore-space-change;;
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ignore-all-space;;
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ignore-space-at-eol;;
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ignore-cr-at-eol;;
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Treats lines with the indicated type of whitespace change as
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unchanged for the sake of a three-way merge. Whitespace
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changes mixed with other changes to a line are not ignored.
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See also linkgit:git-diff[1] `-b`, `-w`,
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`--ignore-space-at-eol`, and `--ignore-cr-at-eol`.
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+
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* If 'their' version only introduces whitespace changes to a line,
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'our' version is used;
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* If 'our' version introduces whitespace changes but 'their'
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version includes a substantial change, 'their' version is used;
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* Otherwise, the merge proceeds in the usual way.
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renormalize;;
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This runs a virtual check-out and check-in of all three stages
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of a file when resolving a three-way merge. This option is
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meant to be used when merging branches with different clean
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filters or end-of-line normalization rules. See "Merging
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branches with differing checkin/checkout attributes" in
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linkgit:gitattributes[5] for details.
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no-renormalize;;
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Disables the `renormalize` option. This overrides the
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`merge.renormalize` configuration variable.
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no-renames;;
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Turn off rename detection. This overrides the `merge.renames`
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configuration variable.
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See also linkgit:git-diff[1] `--no-renames`.
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find-renames[=<n>];;
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Turn on rename detection, optionally setting the similarity
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threshold. This is the default. This overrides the
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'merge.renames' configuration variable.
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See also linkgit:git-diff[1] `--find-renames`.
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rename-threshold=<n>;;
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Deprecated synonym for `find-renames=<n>`.
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subtree[=<path>];;
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This option is a more advanced form of 'subtree' strategy, where
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the strategy makes a guess on how two trees must be shifted to
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match with each other when merging. Instead, the specified path
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is prefixed (or stripped from the beginning) to make the shape of
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two trees to match.
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octopus::
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This resolves cases with more than two heads, but refuses to do
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a complex merge that needs manual resolution. It is
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primarily meant to be used for bundling topic branch
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heads together. This is the default merge strategy when
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pulling or merging more than one branch.
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ours::
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This resolves any number of heads, but the resulting tree of the
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merge is always that of the current branch head, effectively
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ignoring all changes from all other branches. It is meant to
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be used to supersede old development history of side
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branches. Note that this is different from the -Xours option to
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the 'recursive' merge strategy.
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subtree::
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This is a modified recursive strategy. When merging trees A and
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B, if B corresponds to a subtree of A, B is first adjusted to
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match the tree structure of A, instead of reading the trees at
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the same level. This adjustment is also done to the common
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ancestor tree.
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With the strategies that use 3-way merge (including the default, 'recursive'),
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if a change is made on both branches, but later reverted on one of the
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branches, that change will be present in the merged result; some people find
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this behavior confusing. It occurs because only the heads and the merge base
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are considered when performing a merge, not the individual commits. The merge
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algorithm therefore considers the reverted change as no change at all, and
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substitutes the changed version instead.
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