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 ll-merge.h for details.
Low-level (single file) merge
Check ll-merge.h for details.