Uniform iterators for trees, index, and workdir

This create a new git_iterator type of object that provides a
uniform interface for iterating over the index, an arbitrary
tree, or the working directory of a repository.

As part of this, git ignore support was extended to support
push and pop of directory-based ignore files as the working
directory is being traversed (so the array of ignores does
not have to be recreated at each directory during traveral).

There are a number of other small utility functions in buffer,
path, vector, and fileops that are included in this patch
that made the iterator implementation cleaner.

1 files changed, 4 insertions, 0 deletions

diff --git a/tests-clar/diff/diff_helpers.h b/tests-clar/diff/diff_helpers.h
new file mode 100644
index 000000000..a75dd912c
--- /dev/null
+++ b/tests-clar/diff/diff_helpers.h
@@ -0,0 +1,4 @@
+#include "fileops.h"
+
+extern git_tree *resolve_commit_oid_to_tree(
+	git_repository *repo, const char *partial_oid);