buildah treadmill: cleaner YAML, uglier script

There's a stanza in .cirrus.yml that only "runs" in
the treadmill cron job ... but that job is long gone.
The task actually runs in the buildah treadmill PR, #13808,
but that's not obvious to someone reading .cirrus.yml.
This is a maintenance burden. Remove it.

Because rootless bud tests are still important, and we
still want to run them in the treadmill PR, modify the
treadmill script itself so it (ugh) injects rootless jobs
into the buildah_bud test matrix. This is super fragile
but acceptable because I am the only one who ever runs
the treadmill script. I will notice if this breaks.

Signed-off-by: Ed Santiago <santiago@redhat.com>

.cirrus.yml

@@ -995,30 +995,6 @@ buildah_bud_test_task:
     main_script: *main
     always: *int_logs_artifacts
 
-rootless_buildah_bud_test_task:
-    name: *std_name_fmt
-    alias: rootless_buildah_bud_test
-    # Please keep this as-is: the buildah treadmill (#13808) relies on it.
-    only_if: $CIRRUS_CRON == 'treadmill'
-    depends_on:
-        - build
-        - rootless_integration_test
-    env:
-        <<: *stdenvars
-        TEST_FLAVOR: bud
-        PRIV_NAME: rootless
-    matrix:
-        - env:
-            PODBIN_NAME: podman
-        - env:
-            PODBIN_NAME: remote
-    gce_instance: *standardvm
-    timeout_in: 45m
-    clone_script: *get_gosrc
-    setup_script: *setup
-    main_script: *main
-    always: *int_logs_artifacts
-
 upgrade_test_task:
     name: "Upgrade test: from $PODMAN_UPGRADE_FROM"
     alias: upgrade_test
@@ -1125,7 +1101,6 @@ success_task:
         - minikube_test
         - farm_test
         - buildah_bud_test
-        - rootless_buildah_bud_test
         - upgrade_test
         - meta
     container: &smallcontainer

hack/buildah-vendor-treadmill

@@ -372,27 +372,42 @@ sub tweak_cirrus_test_order {
             # of the treadmill PR. Here we switch Cirrus task dependencies
             # such that bud tests run as early as possible.
             if ($current_task =~ /buildah_bud_test/) {
-                # Buildah bud, both root and rootless, now depend on validate
+                # Buildah bud now depends only on validate...
                 $line = "${indent}validate";
             }
             elsif ($2 eq 'validate' && $current_task ne 'success') {
-                # Other tests that relied on validate, now rely on
-                # rootless bud tests instead. The point of the treadmill PR
-                # is to run the bud tests, then rootless bud tests, and
-                # only then, if everything passes, run normal tests.
-                # (Reason: bud tests are the only ones likely to fail,
-                # and we want to see failures early).
-                $line = "${indent}rootless_buildah_bud_test";
+                # ...and all other tests that relied on validate now rely on
+                # bud tests instead. The point of the treadmill PR is to
+                # run the bud tests and only then, if everything passes,
+                # run normal tests. (Reason: bud tests are the only ones
+                # likely to fail on a buildah revendor, and we want to see
+                # failures early).
+                $line = "${indent}buildah_bud_test";
             }
         }
         else {
             undef $in_depend;
 
-            # Rootless tests normally run only on nightly treadmill, but
-            # we really should run them here too. Remove the 'only' clause.
-            if ($current_task eq 'rootless_buildah_bud_test') {
-                if ($line =~ /^\s+only_if:.*treadmill/) {
-                    next;
+            # FIXME THIS IS HORRIBLE!
+            # Add rootless jobs to the buildah bud test matrix.
+            # This is incredibly fragile; it relies on the fact
+            # (true as of 2023-12-07) that the "matrix" yaml lines
+            # are formatted just so and are followed immediately
+            # by a "gce_instance" line.
+            #
+            # Since Ed is the only one who ever runs this script,
+            # he is expected to notice if this ever changes, and
+            # to fix it.
+            if ($current_task eq 'buildah_bud_test') {
+                if ($line =~ /^(\s+)gce_instance:/) {
+                    print { $out } <<'END_ROOTLESS_BUD';
+        - env:
+            PODBIN_NAME: podman
+            PRIV_NAME: rootless
+        - env:
+            PODBIN_NAME: remote
+            PRIV_NAME: rootless
+END_ROOTLESS_BUD
                 }
             }
         }