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`

Check ll-merge.h for details.

Low-level (single file) merge

-----------------------------

Check ll-merge.h for details.