Add sample files and snapshot generator

tests/snapshots/generate_snapshots.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+import itertools
+import subprocess
+import pathlib
+import shutil
+
+def generate_snapshots():
+    single_styles = ["changes", "grid", "header", "numbers"]
+    collective_styles = ["full", "plain"]
+
+    for num in range(len(single_styles)):
+        for grouped in itertools.combinations(single_styles, num + 1):
+            generate_snapshot(",".join(grouped))
+
+    for style in collective_styles:
+        generate_snapshot(style)
+
+def generate_snapshot(option):
+    command = "../../target/debug/bat --style={0} sample.rs > output/{0}.snapshot.txt".format(
+        option
+    )
+    print("generating snapshot for {}".format(option))
+    subprocess.call(command, shell=True)
+
+def prepare_output_dir():
+    shutil.rmtree("output", ignore_errors=True)
+    pathlib.Path("output").mkdir()
+
+def modify_sample_file():
+    print("modifying sample.rs to show changes")
+    shutil.copyfile("sample.modified.rs", "sample.rs")
+
+def undo_sample_file_modification():
+    print("undoing sample.rs modifications")
+    subprocess.call("git checkout -- sample.rs", shell=True)
+
+prepare_output_dir()
+modify_sample_file()
+generate_snapshots()
+undo_sample_file_modification()