changelog: Reference multiple issues/pull requests for a single entry

Update the Change Log template to list multiple issues on separate
lines.

.changelog/2697.internal.md

@@ -0,0 +1,4 @@
+changelog: Reference multiple issues/pull requests for a single entry
+
+For more details, see the description in [Change Log fragments](
+.changelog/README.md#multiple-issues--pull-requests-for-a-single-fragment).

.changelog/README.md

@@ -83,6 +83,27 @@ Example file names:
 - `3456.bugfix.1.md`,
 - `3456.bugfix.2.md`.
 
+## Multiple issues / pull requests for a single fragment
+
+Sometimes referencing multiple issues or pull requests in a Change Log
+fragment is desired.
+
+For example:
+
+- when a single Change Log fragment describes a change that resolves multiple
+  issues, or
+- when a sub-sequent issue / pull request augments a change that already has a
+  corresponding Change Log fragment.
+
+In this case, you need to augment (if necessary) the original Change Log
+fragment (e.g. `1234.feature.md`) and copy it to a new file which has the new
+issue or pull request number in its name (e.g. `1356.feature.md`).
+The [towncrier] tool will automatically detect a duplicate Change Log fragment
+and combine issue / pull request numbers in a single Change Log entry.
+
+_NOTE: You can repeat this process to refer to as many issues / pull requests
+as needed._
+
 ## Render Change Log preview
 
 To get a preview of how your change (and other changes queued up in this

.changelog/template.md.j2

@@ -9,14 +9,15 @@
 
 {% for text, values in sections[section][category].items() %}
 {% set lines = text.splitlines() %}
+{% set referenced_issues = "(" + values | join(',\n   ') + ")" %}
 {% if lines | length > 2 and lines[1] == "" %}
 - {{ lines[0] }}
-  ({{ values | join(', ') }})
+  {{ referenced_issues }}
 
 {{ lines[2:] | join('\n') }}
 {% else %}
 - {{ text }}
-  ({{ values | join(', ') }})
+  {{ referenced_issues }}
 {% endif %}
 {% if not loop.last %}