Closes #84: Strip a lot of newlines in configs (#85)

Author: miaow2

docs/colliecting-diffs.md

@@ -42,6 +42,9 @@ If you have configs in NetBox DataSource, you can define it, the script instead
 !!! note
     Only synced DataSources are acceptable
 
+!!! note
+    Diff replaces sequences of 3 or more empty lines with one empty line
+
 If in your DataSource config names are different from the hostnames of the devices, you can specify config name with Jinja2 template in `Name template` field.
  Reference device with `{{ object }}` variable.
 

netbox_config_diff/compliance/utils.py

@@ -40,8 +40,8 @@ def __init__(self, choices, *args, **kwargs):
 
 def get_unified_diff(rendered_config: str, actual_config: str, device: str) -> str:
     diff = unified_diff(
-        actual_config.splitlines(),
-        rendered_config.strip().splitlines(),
+        re.sub("\n{3,}", "\n", actual_config).splitlines(),
+        re.sub("\n{3,}", "\n", rendered_config).strip().splitlines(),
         fromfiledate=device,
         tofiledate=device,
         lineterm="",