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