Add a diffing function

For now the diff function uses the Linux tool "diff" to generate the diff
since it is efficient and straightforward.

* gn3/computations/diff.py (generate_diff): New function.
* tests/unit/computations/test_diff.py: Test cases for ☝🏾.

1 files changed, 12 insertions, 0 deletions

diff --git a/gn3/computations/diff.py b/gn3/computations/diff.py
new file mode 100644
index 0000000..b5da68a
--- /dev/null
+++ b/gn3/computations/diff.py
@@ -0,0 +1,12 @@
+"""This module contains code that's used for generating diffs"""
+from typing import Optional
+
+from gn3.commands import run_cmd
+
+
+def generate_diff(data: str, edited_data: str) -> Optional[str]:
+    """Generate the diff between 2 files"""
+    results = run_cmd(f"diff {data} {edited_data}")
+    if results.get("code", -1) > 0:
+        return results.get("output")
+    return None