Description of one side of a delta.

Although this is called a "file", it could represent a file, a symbolic link, a submodule commit id, or even a tree (although that only if you are tracking type changes or ignored/untracked directories).

The oid is the git_oid of the item. If the entry represents an absent side of a diff (e.g. the old_file of a GIT_DELTA_ADDED delta), then the oid will be zeroes.

path is the NUL-terminated path to the entry relative to the working directory of the repository.

size is the size of the entry in bytes.

flags is a combination of the git_diff_flag_t types

mode is, roughly, the stat() st_mode value for the item. This will be restricted to one of the git_filemode_t values.