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24d113ec JN |
1 | merge API |
2 | ========= | |
3 | ||
4 | The merge API helps a program to reconcile two competing sets of | |
5 | improvements to some files (e.g., unregistered changes from the work | |
6 | tree versus changes involved in switching to a new branch), reporting | |
7 | conflicts if found. The library called through this API is | |
8 | responsible for a few things. | |
9 | ||
10 | * determining which trees to merge (recursive ancestor consolidation); | |
11 | ||
12 | * lining up corresponding files in the trees to be merged (rename | |
13 | detection, subtree shifting), reporting edge cases like add/add | |
14 | and rename/rename conflicts to the user; | |
15 | ||
16 | * performing a three-way merge of corresponding files, taking | |
17 | path-specific merge drivers (specified in `.gitattributes`) | |
18 | into account. | |
19 | ||
712516bc JN |
20 | Data structures |
21 | --------------- | |
22 | ||
23 | * `mmbuffer_t`, `mmfile_t` | |
24 | ||
25 | These store data usable for use by the xdiff backend, for writing and | |
26 | for reading, respectively. See `xdiff/xdiff.h` for the definitions | |
27 | and `diff.c` for examples. | |
28 | ||
29 | * `struct ll_merge_options` | |
30 | ||
31 | This describes the set of options the calling program wants to affect | |
32 | the operation of a low-level (single file) merge. Some options: | |
33 | ||
34 | `virtual_ancestor`:: | |
35 | Behave as though this were part of a merge between common | |
36 | ancestors in a recursive merge. | |
37 | If a helper program is specified by the | |
38 | `[merge "<driver>"] recursive` configuration, it will | |
fe77b416 | 39 | be used (see linkgit:gitattributes[5]). |
712516bc JN |
40 | |
41 | `variant`:: | |
42 | Resolve local conflicts automatically in favor | |
43 | of one side or the other (as in 'git merge-file' | |
44 | `--ours`/`--theirs`/`--union`). Can be `0`, | |
45 | `XDL_MERGE_FAVOR_OURS`, `XDL_MERGE_FAVOR_THEIRS`, or | |
46 | `XDL_MERGE_FAVOR_UNION`. | |
47 | ||
48 | `renormalize`:: | |
49 | Resmudge and clean the "base", "theirs" and "ours" files | |
50 | before merging. Use this when the merge is likely to have | |
51 | overlapped with a change in smudge/clean or end-of-line | |
52 | normalization rules. | |
53 | ||
24d113ec JN |
54 | Low-level (single file) merge |
55 | ----------------------------- | |
56 | ||
57 | `ll_merge`:: | |
58 | ||
59 | Perform a three-way single-file merge in core. This is | |
60 | a thin wrapper around `xdl_merge` that takes the path and | |
61 | any merge backend specified in `.gitattributes` or | |
62 | `.git/info/attributes` into account. Returns 0 for a | |
63 | clean merge. | |
64 | ||
712516bc | 65 | Calling sequence: |
24d113ec | 66 | |
712516bc JN |
67 | * Prepare a `struct ll_merge_options` to record options. |
68 | If you have no special requests, skip this and pass `NULL` | |
69 | as the `opts` parameter to use the default options. | |
70 | ||
71 | * Allocate an mmbuffer_t variable for the result. | |
72 | ||
73 | * Allocate and fill variables with the file's original content | |
74 | and two modified versions (using `read_mmfile`, for example). | |
75 | ||
76 | * Call `ll_merge()`. | |
77 | ||
78 | * Read the merged content from `result_buf.ptr` and `result_buf.size`. | |
79 | ||
80 | * Release buffers when finished. A simple | |
81 | `free(ancestor.ptr); free(ours.ptr); free(theirs.ptr); | |
82 | free(result_buf.ptr);` will do. | |
24d113ec JN |
83 | |
84 | If the modifications do not merge cleanly, `ll_merge` will return a | |
85 | nonzero value and `result_buf` will generally include a description of | |
86 | the conflict bracketed by markers such as the traditional `<<<<<<<` | |
87 | and `>>>>>>>`. | |
88 | ||
89 | The `ancestor_label`, `our_label`, and `their_label` parameters are | |
90 | used to label the different sides of a conflict if the merge driver | |
91 | supports this. | |
92 | ||
24d113ec JN |
93 | Everything else |
94 | --------------- | |
95 | ||
96 | Talk about <merge-recursive.h> and merge_file(): | |
97 | ||
98 | - merge_trees() to merge with rename detection | |
99 | - merge_recursive() for ancestor consolidation | |
100 | - try_merge_command() for other strategies | |
101 | - conflict format | |
102 | - merge options | |
103 | ||
104 | (Daniel, Miklos, Stephan, JC) |