Update diff to use iterators

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.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/oid.c b/src/oid.c
index 92d8d1e89..a1f010927 100644
--- a/src/oid.c
+++ b/src/oid.c
@@ -190,6 +190,16 @@ int git_oid_streq(const git_oid *a, const char *str)
 	return git_oid_cmp(a, &id) == 0 ? GIT_SUCCESS : GIT_ERROR;
 }
 
+int git_oid_iszero(const git_oid *oid_a)
+{
+	const unsigned char *a = oid_a->id;
+	unsigned int i;
+	for (i = 0; i < GIT_OID_RAWSZ; ++i, ++a)
+		if (*a != 0)
+			return 0;
+	return 1;
+}
+
 typedef short node_index;
 
 typedef union {