Fix incorrect handling of orphan fragment names consists of only digits (#588)

* Don't lose the flag at the start of decimal only orphans
Fixes #584

* Add news fragment

* Reword news fragment to be less git-commenty

* mention why we're removing leading zeros

---------

Co-authored-by: Adi Roiban <[email protected]>

Author: SmileyChris

src/towncrier/_builder.py

@@ -13,15 +13,6 @@
 from jinja2 import Template
 
 
-def strip_if_integer_string(s: str) -> str:
-    try:
-        i = int(s)
-    except ValueError:
-        return s
-
-    return str(i)
-
-
 # Returns ticket, category and counter or (None, None, None) if the basename
 # could not be parsed or doesn't contain a valid category.
 def parse_newfragment_basename(
@@ -45,7 +36,11 @@ def parse_newfragment_basename(
             # NOTE: This allows news fragment names like fix-1.2.3.feature or
             # something-cool.feature.ext for projects that don't use ticket
             # numbers in news fragment names.
-            ticket = strip_if_integer_string(".".join(parts[0:i]))
+            ticket = ".".join(parts[0:i]).strip()
+            # If the ticket is an integer, remove any leading zeros (to resolve
+            # issue #126).
+            if ticket.isdigit():
+                ticket = str(int(ticket))
             counter = 0
             # Use the following part as the counter if it exists and is a valid
             # digit.

src/towncrier/newsfragments/588.bugfix

@@ -0,0 +1 @@
+Orphan news fragments, fragments not associated with an issue, consisting of only digits (e.g. '+12345678.feature') now retain their leading marker character.

src/towncrier/test/test_builder.py

@@ -125,3 +125,10 @@ def test_orphan_with_dotted_number(self):
             parse_newfragment_basename("+orphan_12.3.feature", ["feature"]),
             ("+orphan_12.3", "feature", 0),
         )
+
+    def test_orphan_all_digits(self):
+        """Orphaned snippets can consist of only digits."""
+        self.assertEqual(
+            parse_newfragment_basename("+123.feature", ["feature"]),
+            ("+123", "feature", 0),
+        )