apport-retrace: avoid installing base-files unconditionally

Installing `base-files` is not needed after applying the proper fix for
finding `ld-linux-x86-64.so.2`. So revert installing `base-files` unless
it was requested. In that case install it as first package to corretly
set-up the usrmerge symlinks.

Bug-Ubuntu: https://launchpad.net/bugs/2067120
Fixes: 52560e6 ("apport-retrace: install base-files first")

apport/sandboxutils.py

@@ -120,15 +120,13 @@ def needed_runtime_packages(report, pkgmap_cache_dir, pkg_versions, verbose=Fals
     return [(p, pkg_versions.get(p)) for p in pkgs]
 
 
-def _move_or_add_base_files_first(pkgs: list[tuple[str, None | str]]) -> None:
+def _move_base_files_first(pkgs: list[tuple[str, None | str]]) -> None:
     """Move base-files to the front or add it if missing."""
-    base_files_version = None
     for i, (pkg, version) in enumerate(pkgs):
         if pkg == "base-files":
-            base_files_version = version
             pkgs.pop(i)
-            break
-    pkgs[:0] = [("base-files", base_files_version)]
+            pkgs[:0] = [("base-files", version)]
+            return
 
 
 # pylint: disable-next=too-many-arguments
@@ -234,7 +232,7 @@ def make_sandbox(
             apport.logging.log(f"Origins: {origins}")
 
     # Install base-files first to get correct usrmerge
-    _move_or_add_base_files_first(pkgs)
+    _move_base_files_first(pkgs)
 
     # unpack packages, if any, using cache and sandbox
     try:

tests/unit/test_sandboxutils.py

@@ -17,7 +17,7 @@
 
 from apport.packaging import PackageInfo
 from apport.report import Report
-from apport.sandboxutils import _move_or_add_base_files_first, make_sandbox
+from apport.sandboxutils import _move_base_files_first, make_sandbox
 
 
 class TestSandboxutils(unittest.TestCase):
@@ -72,14 +72,14 @@ def test_make_sandbox_with_sandbox_dir(self, packaging_mock: MagicMock) -> None:
         self.assertEqual(outdated_msg, "obsolete\nobsolete\n")
         self.assertEqual(packaging_mock.install_packages.call_count, 2)
 
-    def test_move_or_add_base_files_first_existing(self) -> None:
-        """_move_or_add_base_files_first() with base-files in list."""
+    def test_move_base_files_first_existing(self) -> None:
+        """_move_base_files_first() with base-files in list."""
         pkgs: list[tuple[str, None | str]] = [
             ("chaos-marmosets", "0.1.2-2"),
             ("base-files", "13ubuntu9"),
             ("libc6", "2.39-0ubuntu8.2"),
         ]
-        _move_or_add_base_files_first(pkgs)
+        _move_base_files_first(pkgs)
         self.assertEqual(
             pkgs,
             [
@@ -89,18 +89,13 @@ def test_move_or_add_base_files_first_existing(self) -> None:
             ],
         )
 
-    def test_move_or_add_base_files_first_missing(self) -> None:
-        """_move_or_add_base_files_first() without base-files in list."""
+    def test_move_base_files_first_missing(self) -> None:
+        """_move_base_files_first() without base-files in list."""
         pkgs: list[tuple[str, None | str]] = [
             ("chaos-marmosets", "0.1.2-2"),
             ("libc6", "2.39-0ubuntu8.2"),
         ]
-        _move_or_add_base_files_first(pkgs)
+        _move_base_files_first(pkgs)
         self.assertEqual(
-            pkgs,
-            [
-                ("base-files", None),
-                ("chaos-marmosets", "0.1.2-2"),
-                ("libc6", "2.39-0ubuntu8.2"),
-            ],
+            pkgs, [("chaos-marmosets", "0.1.2-2"), ("libc6", "2.39-0ubuntu8.2")]
         )