test(docker): force the dup path in the Update-repo probe

Author: qwO-Owp

.github/workflows/exp-opensuse.yml

@@ -1,5 +1,6 @@
 # Throwaway experiment (deleted after it runs): proves the fix in
 # docker/Dockerfile by forcing openSUSE-Tumbleweed-Update unreachable.
+# A dup --dry-run before the install forces the code path that failed:
 # "fixed" must build; "mutant" (the pre-fix Dockerfile) must fail.
 name: exp-opensuse
 on:
@@ -28,9 +29,13 @@ jobs:
           assert s.count(key) == 1, 'anchor missing'
           bad = ('\t\tzypper --non-interactive modifyrepo --url '
                  'http://invalid.invalid/ openSUSE-Tumbleweed-Update; \\\n')
-          open(p, 'w').write(s.replace(key, bad + key))
+          s = s.replace(key, bad + key)
+          k2 = '\t\tpkgs="gcc clang'
+          assert s.count(k2) == 1, 'pkgs anchor missing'
+          dup = '\t\tzypper --non-interactive dup --dry-run --no-recommends; \\\n'
+          open(p, 'w').write(s.replace(k2, dup + k2))
           PY
-          grep -n 'invalid.invalid' docker/Dockerfile
+          grep -nE 'invalid.invalid|dry-run' docker/Dockerfile
           set +e
           docker build -f docker/Dockerfile -t probe \
             --build-arg BASE=opensuse/tumbleweed --build-arg CC=gcc \