merge-recursive: options to ignore whitespace changes
[git/git.git] / Documentation / merge-strategies.txt
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1MERGE STRATEGIES
2----------------
3
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4The merge mechanism ('git-merge' and 'git-pull' commands) allows the
5backend 'merge strategies' to be chosen with `-s` option. Some strategies
6can also take their own options, which can be passed by giving `-X<option>`
7arguments to 'git-merge' and/or 'git-pull'.
8
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9resolve::
10 This can only resolve two heads (i.e. the current branch
4fa535a1 11 and another branch you pulled from) using a 3-way merge
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12 algorithm. It tries to carefully detect criss-cross
13 merge ambiguities and is considered generally safe and
9688a882 14 fast.
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15
16recursive::
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17 This can only resolve two heads using a 3-way merge
18 algorithm. When there is more than one common
19 ancestor that can be used for 3-way merge, it creates a
9688a882 20 merged tree of the common ancestors and uses that as
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21 the reference tree for the 3-way merge. This has been
22 reported to result in fewer merge conflicts without
23 causing mis-merges by tests done on actual merge commits
24 taken from Linux 2.6 kernel development history.
25 Additionally this can detect and handle merges involving
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26 renames. This is the default merge strategy when
27 pulling or merging one branch.
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28+
29The 'recursive' strategy can take the following options:
30
31ours;;
32 This option forces conflicting hunks to be auto-resolved cleanly by
33 favoring 'our' version. Changes from the other tree that do not
34 conflict with our side are reflected to the merge result.
35+
36This should not be confused with the 'ours' merge strategy, which does not
37even look at what the other tree contains at all. It discards everything
38the other tree did, declaring 'our' history contains all that happened in it.
39
40theirs;;
41 This is opposite of 'ours'.
42
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43patience;;
44 With this option, 'merge-recursive' spends a little extra time
45 to avoid mismerges that sometimes occur due to unimportant
46 matching lines (e.g., braces from distinct functions). Use
47 this when the branches to be merged have diverged wildly.
48 See also linkgit:git-diff[1] `--patience`.
49
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50ignore-space-change;;
51ignore-all-space;;
52ignore-space-at-eol;;
53 Treats lines with the indicated type of whitespace change as
54 unchanged for the sake of a three-way merge. Whitespace
55 changes mixed with other changes to a line are not ignored.
56 See also linkgit:git-diff[1] `-b`, `-w`, and
57 `--ignore-space-at-eol`.
58+
59* If 'their' version only introduces whitespace changes to a line,
60 'our' version is used;
61* If 'our' version introduces whitespace changes but 'their'
62 version includes a substantial change, 'their' version is used;
63* Otherwise, the merge proceeds in the usual way.
64
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65renormalize;;
66 This runs a virtual check-out and check-in of all three stages
67 of a file when resolving a three-way merge. This option is
68 meant to be used when merging branches with different clean
69 filters or end-of-line normalization rules. See "Merging
70 branches with differing checkin/checkout attributes" in
71 linkgit:gitattributes[5] for details.
72
73no-renormalize;;
74 Disables the `renormalize` option. This overrides the
75 `merge.renormalize` configuration variable.
76
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77subtree[=path];;
78 This option is a more advanced form of 'subtree' strategy, where
79 the strategy makes a guess on how two trees must be shifted to
80 match with each other when merging. Instead, the specified path
81 is prefixed (or stripped from the beginning) to make the shape of
82 two trees to match.
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83
84octopus::
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85 This resolves cases with more than two heads, but refuses to do
86 a complex merge that needs manual resolution. It is
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87 primarily meant to be used for bundling topic branch
88 heads together. This is the default merge strategy when
4fa535a1 89 pulling or merging more than one branch.
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90
91ours::
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92 This resolves any number of heads, but the resulting tree of the
93 merge is always that of the current branch head, effectively
94 ignoring all changes from all other branches. It is meant to
bb73d73c 95 be used to supersede old development history of side
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96 branches. Note that this is different from the -Xours option to
97 the 'recursive' merge strategy.
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98
99subtree::
100 This is a modified recursive strategy. When merging trees A and
101 B, if B corresponds to a subtree of A, B is first adjusted to
102 match the tree structure of A, instead of reading the trees at
103 the same level. This adjustment is also done to the common
104 ancestor tree.