operations/crontab: fix replace containing newline, add test

This replace is triggered e.g. when replacing an (pre-)existing crontab
line without name to one maintained by pyinfra, this time with a
pyinfra-name.

The sed replace command contains a newline character that should stay as
a '\n' and not an actual newline, as sed does not support a multi-line
script.

Author: Nananas

pyinfra/operations/crontab.py

@@ -157,7 +157,7 @@ def comma_sep(value):
             ),
         ):
             if not exists_name and cron_name:
-                new_crontab_line = f"{name_comment}\n{new_crontab_line}"
+                new_crontab_line = f"{name_comment}\\n{new_crontab_line}"
             edit_commands.append(
                 sed_replace(
                     temp_filename,

tests/operations/crontab.crontab/edit_existing_with_newline.json

@@ -0,0 +1,26 @@
+{
+    "args": ["command_to_be"],
+    "kwargs": {
+        "month": 1,
+        "cron_name": "name of cron"
+    },
+    "facts": {
+        "crontab.Crontab": {
+            "user=None": {
+                "command_to_be": {
+                    "minute": "*",
+                    "hour": "*",
+                    "month": "*",
+                    "day_of_week": "*",
+                    "day_of_month": "*",
+                    "comments": []
+                }
+            }
+        }
+    },
+    "commands": [
+        "crontab -l  > _tempfile_",
+        "sed -i.a-timestamp 's/.*command_to_be.*/# pyinfra-name=name of cron\\n* * * 1 * command_to_be/' _tempfile_ && rm -f _tempfile_.a-timestamp",
+        "crontab  _tempfile_"
+    ]
+}