If a merge is in progress, invoke 'callback' for each commit ID in the MERGE_HEAD file.
Return a non-zero value from the callback to stop the loop.
A repository object
Callback function
Pointer to callback data (optional)
0 on success, non-zero callback return value, git_error_code.GIT_ENOTFOUND if there is no MERGE_HEAD file, or other error code.
See Implementation
If a merge is in progress, invoke 'callback' for each commit ID in the MERGE_HEAD file.
Return a non-zero value from the callback to stop the loop.