# merge API

2025-05-28

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`

Check merge-ll.h for details.

## Low-level (single file) merge

Check merge-ll.h for details.