Initial implementation of diff rename detection

This implements the basis for diff rename and copy detection,
although it is based on simple SHA comparison right now instead
of using a matching algortihm.  Just as `git_diff_merge` can be
used as a post-pass on diffs to emulate certain command line
behaviors, there is a new API `git_diff_detect` which will
update a diff list in-place, adjusting some deltas to RENAMED
or COPIED state (and also, eventually, splitting MODIFIED deltas
where the change is too large into DELETED/ADDED pairs).

This also adds a new test repo that will hold rename/copy/split
scenarios.  Right now, it just has exact-match rename and copy,
but the tests are written to use tree diffs, so we should be able
to add new test scenarios easily without breaking tests.

1 files changed, 5 insertions, 12 deletions

diff --git a/tests-clar/diff/diff_helpers.c b/tests-clar/diff/diff_helpers.c
index de0e7e074..992c87d4c 100644
--- a/tests-clar/diff/diff_helpers.c
+++ b/tests-clar/diff/diff_helpers.c
@@ -32,20 +32,13 @@ int diff_file_fn(
 
 	e->files++;
 
-	if (delta->binary) {
-		e->at_least_one_of_them_is_binary = true;
+	if (delta->binary)
 		e->files_binary++;
-	}
 
-	switch (delta->status) {
-	case GIT_DELTA_ADDED: e->file_adds++; break;
-	case GIT_DELTA_DELETED: e->file_dels++; break;
-	case GIT_DELTA_MODIFIED: e->file_mods++; break;
-	case GIT_DELTA_IGNORED: e->file_ignored++; break;
-	case GIT_DELTA_UNTRACKED: e->file_untracked++; break;
-	case GIT_DELTA_UNMODIFIED: e->file_unmodified++; break;
-	default: break;
-	}
+	cl_assert(delta->status <= GIT_DELTA_TYPECHANGE);
+
+	e->file_status[delta->status] += 1;
+
 	return 0;
 }