104 lines
3.3 KiB
Text
104 lines
3.3 KiB
Text
merge API
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=========
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The merge API helps a program to reconcile two competing sets of
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improvements to some files (e.g., unregistered changes from the work
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tree versus changes involved in switching to a new branch), reporting
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conflicts if found. The library called through this API is
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responsible for a few things.
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* determining which trees to merge (recursive ancestor consolidation);
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* lining up corresponding files in the trees to be merged (rename
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detection, subtree shifting), reporting edge cases like add/add
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and rename/rename conflicts to the user;
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* performing a three-way merge of corresponding files, taking
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path-specific merge drivers (specified in `.gitattributes`)
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into account.
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Data structures
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---------------
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* `mmbuffer_t`, `mmfile_t`
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These store data usable for use by the xdiff backend, for writing and
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for reading, respectively. See `xdiff/xdiff.h` for the definitions
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and `diff.c` for examples.
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* `struct ll_merge_options`
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This describes the set of options the calling program wants to affect
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the operation of a low-level (single file) merge. Some options:
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`virtual_ancestor`::
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Behave as though this were part of a merge between common
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ancestors in a recursive merge.
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If a helper program is specified by the
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`[merge "<driver>"] recursive` configuration, it will
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be used (see linkgit:gitattributes[5]).
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`variant`::
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Resolve local conflicts automatically in favor
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of one side or the other (as in 'git merge-file'
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`--ours`/`--theirs`/`--union`). Can be `0`,
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`XDL_MERGE_FAVOR_OURS`, `XDL_MERGE_FAVOR_THEIRS`, or
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`XDL_MERGE_FAVOR_UNION`.
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`renormalize`::
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Resmudge and clean the "base", "theirs" and "ours" files
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before merging. Use this when the merge is likely to have
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overlapped with a change in smudge/clean or end-of-line
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normalization rules.
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Low-level (single file) merge
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-----------------------------
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`ll_merge`::
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Perform a three-way single-file merge in core. This is
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a thin wrapper around `xdl_merge` that takes the path and
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any merge backend specified in `.gitattributes` or
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`.git/info/attributes` into account. Returns 0 for a
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clean merge.
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Calling sequence:
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* Prepare a `struct ll_merge_options` to record options.
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If you have no special requests, skip this and pass `NULL`
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as the `opts` parameter to use the default options.
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* Allocate an mmbuffer_t variable for the result.
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* Allocate and fill variables with the file's original content
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and two modified versions (using `read_mmfile`, for example).
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* Call `ll_merge()`.
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* Read the merged content from `result_buf.ptr` and `result_buf.size`.
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* Release buffers when finished. A simple
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`free(ancestor.ptr); free(ours.ptr); free(theirs.ptr);
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free(result_buf.ptr);` will do.
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If the modifications do not merge cleanly, `ll_merge` will return a
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nonzero value and `result_buf` will generally include a description of
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the conflict bracketed by markers such as the traditional `<<<<<<<`
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and `>>>>>>>`.
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The `ancestor_label`, `our_label`, and `their_label` parameters are
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used to label the different sides of a conflict if the merge driver
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supports this.
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Everything else
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---------------
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Talk about <merge-recursive.h> and merge_file():
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- merge_trees() to merge with rename detection
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- merge_recursive() for ancestor consolidation
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- try_merge_command() for other strategies
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- conflict format
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- merge options
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(Daniel, Miklos, Stephan, JC)
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