feat(patch): add bindings and api

test/blob_test.dart

@@ -96,5 +96,82 @@ void main() {
 
       newBlob.free();
     });
+
+    group('diff', () {
+      const path = 'feature_file';
+      const oldBlobSha = 'e69de29bb2d1d6434b8b29ae775ad8c2e48c5391';
+      const newBlobSha = '9c78c21d6680a7ffebc76f7ac68cacc11d8f48bc';
+      const blobPatch = """
+diff --git a/feature_file b/feature_file
+index e69de29..9c78c21 100644
+--- a/feature_file
++++ b/feature_file
+@@ -0,0 +1 @@
++Feature edit
+""";
+
+      const blobPatchDelete = """
+diff --git a/feature_file b/feature_file
+deleted file mode 100644
+index e69de29..0000000
+--- a/feature_file
++++ /dev/null
+""";
+      test('successfully creates from blobs', () {
+        final a = repo[oldBlobSha] as Blob;
+        final b = repo[newBlobSha] as Blob;
+        final patch = repo.diffBlobs(
+          a: a,
+          b: b,
+          aPath: path,
+          bPath: path,
+        );
+
+        expect(patch.text, blobPatch);
+
+        patch.free();
+      });
+
+      test('successfully creates from one blob (delete)', () {
+        final a = repo[oldBlobSha] as Blob;
+        final patch = a.diff(
+          newBlob: null,
+          oldAsPath: path,
+          newAsPath: path,
+        );
+
+        expect(patch.text, blobPatchDelete);
+
+        patch.free();
+      });
+
+      test('successfully creates from blob and buffer', () {
+        final a = repo[oldBlobSha] as Blob;
+        final patch = Patch.createFrom(
+          a: a,
+          b: 'Feature edit\n',
+          aPath: path,
+          bPath: path,
+        );
+
+        expect(patch.text, blobPatch);
+
+        patch.free();
+      });
+
+      test('successfully creates from blob and buffer (delete)', () {
+        final a = repo[oldBlobSha] as Blob;
+        final patch = Patch.createFrom(
+          a: a,
+          b: null,
+          aPath: path,
+          bPath: path,
+        );
+
+        expect(patch.text, blobPatchDelete);
+
+        patch.free();
+      });
+    });
   });
 }