git expects an empty line after the binary data:

literal X
...binary data...
<empty_line>

The last literal block of the generated patches were not containing the required empty line. Example:

	diff --git a/binary_file b/binary_file
	index 3f1b3f9098131cfecea4a50ff8afab349ea66d22..86e5c1008b5ce635d3e3fffa4434c5eccd8f00b6 100644
	GIT binary patch
	literal 8
	Pc${NM&PdElPvrst3ey5{

	literal 6
	Nc${NM%g@i}0ssZ|0lokL
	diff --git a/binary_file2 b/binary_file2
	index 31be99be19470da4af5b28b21e27896a2f2f9ee2..86e5c1008b5ce635d3e3fffa4434c5eccd8f00b6 100644
	GIT binary patch
	literal 8
	Pc${NM&PdElPvrst3ey5{

	literal 13
	Sc${NMEKbZyOexL+Qd|HZV+4u-

git apply of that diff results in:

	error: corrupt binary patch at line 9: diff --git a/binary_file2 b/binary_file2
	fatal: patch with only garbage at line 10

The proper formating is:

	diff --git a/binary_file b/binary_file
	index 3f1b3f9098131cfecea4a50ff8afab349ea66d22..86e5c1008b5ce635d3e3fffa4434c5eccd8f00b6 100644
	GIT binary patch
	literal 8
	Pc${NM&PdElPvrst3ey5{

	literal 6
	Nc${NM%g@i}0ssZ|0lokL
	diff --git a/binary_file2 b/binary_file2
	index 31be99be19470da4af5b28b21e27896a2f2f9ee2..86e5c1008b5ce635d3e3fffa4434c5eccd8f00b6 100644
	GIT binary patch
	literal 8
	Pc${NM&PdElPvrst3ey5{

	literal 13
	Sc${NMEKbZyOexL+Qd|HZV+4u-

Introduce a new binary diff callback to provide the actual binary
delta contents to callers.  Create this data from the diff contents
(instead of directly from the ODB) to support binary diffs including
the workdir, not just things coming out of the ODB.

Decode base64-encoded text into a git_buf

Conflicts:
	include/git2/diff.h