4 This document describes the outcomes of the trivial merge logic in read-tree.
9 This replaces the index with a different tree, keeping the stat info
10 for entries that don't change, and allowing -u to make the minimum
11 required changes to the working tree to have it match.
14 -----------------------
28 It is permitted for the index to lack an entry; this does not prevent
29 any case from applying.
31 If the index exists, it is an error for it not to match either the
32 head or (if the merge is trivial) the result.
34 If multiple cases apply, the one used is listed first.
36 A result of "no merge" means that index is left in stage 0, ancest in
37 stage 1, head in stage 2, and remote in stage 3 (if any of these are
38 empty, no entry is left for that stage). Otherwise, the given entry is
39 left in stage 0, and there are no other entries.
41 A result of "no merge" is an error if the index is not empty and not
44 *empty* means that the tree must not have a directory-file conflict
47 For multiple ancestors or remotes, a '+' means that this case applies
48 even if only one ancestor or remote fits; normally, all of the
49 ancestors or remotes must be the same.
51 case ancest head remote result
52 ----------------------------------------
53 1 (empty)+ (empty) (empty) (empty)
54 2ALT (empty)+ *empty* remote remote
55 2ALT (empty)+ *empty* remote remote
56 2 (empty)^ (empty) remote no merge
57 3ALT (empty)+ head *empty* head
58 3 (empty)^ head (empty) no merge
59 4 (empty)^ head remote no merge
61 6 ancest^ (empty) (empty) no merge
62 8ALT ancest (empty) ancest (empty)
63 7 ancest+ (empty) remote no merge
64 9 ancest+ head (empty) no merge
65 10ALT ancest ancest (empty) (empty)
66 11 ancest+ head remote no merge
67 16 anc1/anc2 anc1 anc2 no merge
68 13 ancest+ head ancest head
69 14 ancest+ ancest remote remote
70 14ALT ancest+ ancest remote remote
72 Only #2ALT and #3ALT use *empty*, because these are the only cases
73 where there can be conflicts that didn't exist before. Note that we
74 allow directory-file conflicts between things in different stages
75 after the trivial merge.
77 A possible alternative for #6 is (empty), which would make it like
78 #1. This is not used, due to the likelihood that it arises due to
79 moving the file to multiple different locations or moving and deleting
80 it in different branches.
82 Case #1 is included for completeness, and also in case we decide to
83 put on '+' markings; any path that is never mentioned at all isn't
86 Note that #16 is when both #13 and #14 apply; in this case, we refuse
87 the trivial merge, because we can't tell from this data which is
88 right. This is a case of a reverted patch (in some direction, maybe
89 multiple times), and the right answer depends on looking at crossings
90 of history or common ancestors of the ancestors.
92 The status as of Sep 5 is that multiple remotes are not supported