debian: support additional suites

Fixes #1755

Author: Noah Meyerhans

mkosi/distribution/debian.py

@@ -41,7 +41,19 @@ def package_manager(cls, config: Config) -> type[Apt]:
     @classmethod
     def repositories(cls, context: Context, for_image: bool = False) -> Iterable[AptRepository]:
         types = ("deb", "deb-src")
-        components = ("main", *context.config.repositories)
+        components = ("main", *[s for s in context.config.repositories if ":" not in s])
+        suite_components = {}
+        for s in context.config.repositories:
+            if ":" not in s:
+                components += (s,)
+            else:
+                key, value = s.split(":", 1)
+                if key not in suite_components:
+                    suite_components[key] = [value]
+                else:
+                    #suite_components[key] += (value,)
+                    suite_components[key].append(value)
+
         mirror = None if for_image else context.config.mirror
         snapshot = None if for_image else context.config.snapshot
 
@@ -77,6 +89,19 @@ def repositories(cls, context: Context, for_image: bool = False) -> Iterable[Apt
             signedby=signedby,
         )
 
+        for suite, comps in suite_components.items():
+            if snapshot:
+                url = join_mirror(mirror, f"archive/{suite}/{snapshot}")
+            else:
+                url = join_mirror(mirror, "debian")
+            yield AptRepository(
+                types=types,
+                url=url,
+                suite=suite,
+                components=tuple(comps),
+                signedby=signedby,
+            )
+
         # Debug repos are typically not mirrored.
         if snapshot:
             url = join_mirror(mirror, f"archive/debian-debug/{snapshot}")

mkosi/resources/man/mkosi.1.md

@@ -587,7 +587,8 @@ boolean argument: either `1`, `yes`, or `true` to enable, or `0`, `no`,
 
 `Repositories=`, `--repositories=`
 :   Enable package repositories that are disabled by default. This can be used to enable the EPEL repos for
-    CentOS or different components of the Debian/Kali/Ubuntu repositories.
+    CentOS or different components of the Debian/Kali/Ubuntu repositories.  Debian suites can be specified
+    ahead of the component, separated by a ":" (colon) character, e.g. `trixie-backports:main`.
 
 ### [Output] Section