[Resolve Sceptre#1498] Tweak diff output

In order to produce output that does not confuse syntax highlighters
that recognise diff-formatted output, it is decided here to replace the
"-" character (which would often cause a diff highlighter to colour the
line as red) instead with "~" which would tend to be ignored by diff
highlighters.

sceptre/cli/diff.py

@@ -189,12 +189,12 @@ def output_buffer_with_normalized_bar_lengths(
     max_length = len(max(buffer, key=len))
     buffer.seek(0)
     full_length_star_bar = "*" * max_length
-    full_length_line_bar = "-" * max_length
+    full_length_tilde_bar = "~" * max_length
     for line in buffer:
         if DiffWriter.STAR_BAR in line:
             line = line.replace(DiffWriter.STAR_BAR, full_length_star_bar)
-        if DiffWriter.LINE_BAR in line:
-            line = line.replace(DiffWriter.LINE_BAR, full_length_line_bar)
+        if DiffWriter.TILDE_BAR in line:
+            line = line.replace(DiffWriter.TILDE_BAR, full_length_tilde_bar)
         output_stream.write(line)
 
 

sceptre/diffing/diff_writer.py

@@ -25,7 +25,7 @@ class DiffWriter(Generic[DiffType]):
     """
 
     STAR_BAR = "*" * 80
-    LINE_BAR = "-" * 80
+    TILDE_BAR = "~" * 80
 
     def __init__(
         self, stack_diff: StackDiff, output_stream: TextIO, output_format: str
@@ -59,26 +59,26 @@ def write(self):
             self._output(f"No difference to deployed stack {self.stack_name}")
             return
 
-        self._output(f"--> Difference detected for stack {self.stack_name}!")
+        self._output(f"==> Difference detected for stack {self.stack_name}!")
 
         if not self.is_deployed:
             self._write_new_stack_details()
             return
 
-        self._output(self.LINE_BAR)
+        self._output(self.TILDE_BAR)
         self._write_config_difference()
-        self._output(self.LINE_BAR)
+        self._output(self.TILDE_BAR)
         self._write_template_difference()
 
     def _write_new_stack_details(self):
         stack_config_text = self._dump_stack_config(self.stack_diff.generated_config)
         self._output(
             "This stack is not deployed yet!",
-            self.LINE_BAR,
+            self.TILDE_BAR,
             "New Config:",
             "",
             stack_config_text,
-            self.LINE_BAR,
+            self.TILDE_BAR,
             "New Template:",
             "",
             self.stack_diff.generated_template,

tests/test_diffing/test_diff_writer.py

@@ -57,7 +57,7 @@ def setup_method(self, method):
         self.output_stream = StringIO()
 
         self.diff_detected_message = (
-            f"--> Difference detected for stack {self.stack_name}!"
+            f"==> Difference detected for stack {self.stack_name}!"
         )
 
     @property
@@ -133,11 +133,11 @@ def test_write__new_stack__writes_new_stack_config_and_template(
             DiffWriter.STAR_BAR,
             self.diff_detected_message,
             "This stack is not deployed yet!",
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             "New Config:",
             "",
             config_serializer(dict(self.generated_config._asdict())),
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             "New Template:",
             "",
             self.generated_template,
@@ -152,11 +152,11 @@ def test_write__only_config_is_different__writes_config_difference(self):
         self.assert_expected_output(
             DiffWriter.STAR_BAR,
             self.diff_detected_message,
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             f"Config difference for {self.stack_name}:",
             "",
             self.diff_output,
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             "No template difference",
         )
 
@@ -169,9 +169,9 @@ def test_write__only_template_is_different__writes_template_difference(self):
         self.assert_expected_output(
             DiffWriter.STAR_BAR,
             self.diff_detected_message,
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             "No stack config difference",
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             f"Template difference for {self.stack_name}:",
             "",
             self.diff_output,
@@ -186,11 +186,11 @@ def test_write__config_and_template_are_different__writes_both_differences(self)
         self.assert_expected_output(
             DiffWriter.STAR_BAR,
             self.diff_detected_message,
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             f"Config difference for {self.stack_name}:",
             "",
             self.diff_output,
-            DiffWriter.LINE_BAR,
+            DiffWriter.TILDE_BAR,
             f"Template difference for {self.stack_name}:",
             "",
             self.diff_output,