In-memory representation of a file entry in the index.

This is a public structure that represents a file entry in the index. The meaning of the fields corresponds to core Git's documentation (in "Documentation/technical/index-format.txt").

The flags field consists of a number of bit fields which can be accessed via the first set of GIT_IDXENTRY_... bitmasks below. These flags are all read from and persisted to disk.

The flags_extended field also has a number of bit fields which can be accessed via the later GIT_IDXENTRY_... bitmasks below. Some of these flags are read from and written to disk, but some are set aside for in-memory only reference.