This reverts the changes to the GIT_STATUS constants and adds a
new enumeration to describe the type of change in a git_diff_delta.
I don't love this solution, but it should prevent strange errors
from occurring for now. Eventually, I would like to unify the
various status constants, but it needs a larger plan and I just
wanted to eliminate this breakage quickly.
This is a major reorganization of the diff code. This changes
the diff functions to use the iterators for traversing the
content. This allowed a lot of code to be simplified. Also,
this moved the functions relating to outputting a diff into a
new file (diff_output.c).
This includes a number of other changes - adding utility
functions, extending iterators, etc. plus more tests for the
diff code. This also takes the example diff.c program much
further in terms of emulating git-diff command line options.
