Error messages should be sentence fragments, and therefore:
1. Should not begin with a capital letter,
2. Should not conclude with punctuation, and
3. Should not end a sentence and begin a new one
When creating and printing diffs, deal with binary deltas that have
binary data specially, versus diffs that have a binary file but lack the
actual binary data.
Patches can now come from a variety of sources - either internally
generated (from diffing two commits) or as the results of parsing
some external data.
Handle the application of binary patches. Include tests that
produce a binary patch (an in-memory `git_patch` object),
then enusre that the patch applies correctly.
