Documentation/merge-strategies.txt

   1 MERGE STRATEGIES
   2 ----------------
   3
   4 The merge mechanism (`git merge` and `git pull` commands) allows the
   5 backend 'merge strategies' to be chosen with `-s` option.  Some strategies
   6 can also take their own options, which can be passed by giving `-X<option>`
   7 arguments to `git merge` and/or `git pull`.
   8
   9 resolve::
  10         This can only resolve two heads (i.e. the current branch
  11         and another branch you pulled from) using a 3-way merge
  12         algorithm.  It tries to carefully detect criss-cross
  13         merge ambiguities and is considered generally safe and
  14         fast.
  15
  16 recursive::
  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
  20         merged tree of the common ancestors and uses that as
  21         the reference tree for the 3-way merge.  This has been
  22         reported to result in fewer merge conflicts without
  23         causing mismerges 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
  26         renames, but currently cannot make use of detected
  27         copies.  This is the default merge strategy when pulling
  28         or merging one branch.
  29 +
  30 The 'recursive' strategy can take the following options:
  31
  32 ours;;
  33         This option forces conflicting hunks to be auto-resolved cleanly by
  34         favoring 'our' version.  Changes from the other tree that do not
  35         conflict with our side are reflected to the merge result.
  36         For a binary file, the entire contents are taken from our side.
  37 +
  38 This should not be confused with the 'ours' merge strategy, which does not
  39 even look at what the other tree contains at all.  It discards everything
  40 the other tree did, declaring 'our' history contains all that happened in it.
  41
  42 theirs;;
  43         This is the opposite of 'ours'; note that, unlike 'ours', there is
  44         no 'theirs' merge strategy to confuse this merge option with.
  45
  46 patience;;
  47         With this option, 'merge-recursive' spends a little extra time
  48         to avoid mismerges that sometimes occur due to unimportant
  49         matching lines (e.g., braces from distinct functions).  Use
  50         this when the branches to be merged have diverged wildly.
  51         See also linkgit:git-diff[1] `--patience`.
  52
  53 diff-algorithm=[patience|minimal|histogram|myers];;
  54         Tells 'merge-recursive' to use a different diff algorithm, which
  55         can help avoid mismerges that occur due to unimportant matching
  56         lines (such as braces from distinct functions).  See also
  57         linkgit:git-diff[1] `--diff-algorithm`.
  58
  59 ignore-space-change;;
  60 ignore-all-space;;
  61 ignore-space-at-eol;;
  62 ignore-cr-at-eol;;
  63         Treats lines with the indicated type of whitespace change as
  64         unchanged for the sake of a three-way merge.  Whitespace
  65         changes mixed with other changes to a line are not ignored.
  66         See also linkgit:git-diff[1] `-b`, `-w`,
  67         `--ignore-space-at-eol`, and `--ignore-cr-at-eol`.
  68 +
  69 * If 'their' version only introduces whitespace changes to a line,
  70   'our' version is used;
  71 * If 'our' version introduces whitespace changes but 'their'
  72   version includes a substantial change, 'their' version is used;
  73 * Otherwise, the merge proceeds in the usual way.
  74
  75 renormalize;;
  76         This runs a virtual check-out and check-in of all three stages
  77         of a file when resolving a three-way merge.  This option is
  78         meant to be used when merging branches with different clean
  79         filters or end-of-line normalization rules.  See "Merging
  80         branches with differing checkin/checkout attributes" in
  81         linkgit:gitattributes[5] for details.
  82
  83 no-renormalize;;
  84         Disables the `renormalize` option.  This overrides the
  85         `merge.renormalize` configuration variable.
  86
  87 no-renames;;
  88         Turn off rename detection. This overrides the `merge.renames`
  89         configuration variable.
  90         See also linkgit:git-diff[1] `--no-renames`.
  91
  92 find-renames[=<n>];;
  93         Turn on rename detection, optionally setting the similarity
  94         threshold.  This is the default. This overrides the
  95         'merge.renames' configuration variable.
  96         See also linkgit:git-diff[1] `--find-renames`.
  97
  98 rename-threshold=<n>;;
  99         Deprecated synonym for `find-renames=<n>`.
 100
 101 subtree[=<path>];;
 102         This option is a more advanced form of 'subtree' strategy, where
 103         the strategy makes a guess on how two trees must be shifted to
 104         match with each other when merging.  Instead, the specified path
 105         is prefixed (or stripped from the beginning) to make the shape of
 106         two trees to match.
 107
 108 octopus::
 109         This resolves cases with more than two heads, but refuses to do
 110         a complex merge that needs manual resolution.  It is
 111         primarily meant to be used for bundling topic branch
 112         heads together.  This is the default merge strategy when
 113         pulling or merging more than one branch.
 114
 115 ours::
 116         This resolves any number of heads, but the resulting tree of the
 117         merge is always that of the current branch head, effectively
 118         ignoring all changes from all other branches.  It is meant to
 119         be used to supersede old development history of side
 120         branches.  Note that this is different from the -Xours option to
 121         the 'recursive' merge strategy.
 122
 123 subtree::
 124         This is a modified recursive strategy. When merging trees A and
 125         B, if B corresponds to a subtree of A, B is first adjusted to
 126         match the tree structure of A, instead of reading the trees at
 127         the same level. This adjustment is also done to the common
 128         ancestor tree.
 129
 130 With the strategies that use 3-way merge (including the default, 'recursive'),
 131 if a change is made on both branches, but later reverted on one of the
 132 branches, that change will be present in the merged result; some people find
 133 this behavior confusing.  It occurs because only the heads and the merge base
 134 are considered when performing a merge, not the individual commits.  The merge
 135 algorithm therefore considers the reverted change as no change at all, and
 136 substitutes the changed version instead.