feat(e2e): drop a known-failure marker once the commit under test has the fix

The runner reads the commit from the binaries' commit file and asks git
whether it contains the fix of the bug a marker is for, so the same runner
tests a branch with the bug and one without it.

e2e/platforms/qemu_windows/run.py

@@ -110,6 +110,25 @@ def _with(fn, **kwargs):
     return step
 
 
+def _contains(fix: str) -> bool:
+    """Whether the commit under test has the commit `fix` in its history, so that
+    a marker for the bug it fixed no longer applies. Not known: no."""
+    commit = os.environ.get("KOMOREBI_E2E_COMMIT")
+    if not commit:
+        return False
+    here = Path(__file__).resolve().parent
+    git = subprocess.run(
+        ["git", "-C", str(here), "merge-base", "--is-ancestor", fix, commit],
+        capture_output=True,
+    )
+    return git.returncode == 0
+
+
+# the commit that fixed each bug a marker is for (komorebi's `next`)
+UNKNOWN_MONITOR_FIX = "837ca257"
+PLACEMENT_INTEGER_FIX = "3b424dd7"
+
+
 def _commit() -> str:
     """The kfw commit under test: set `KOMOREBI_E2E_COMMIT` to the commit the
     binaries were built from; otherwise this tree's HEAD, which may not be it."""
@@ -331,7 +350,9 @@ def run_one(
                     run_suite(checks, shared(
                         _with(
                             commands.unknown_monitor,
-                            known_failure=UNKNOWN_MONITOR_BUG,
+                            known_failure=None
+                            if _contains(UNKNOWN_MONITOR_FIX)
+                            else UNKNOWN_MONITOR_BUG,
                         ),
                         platform, checks, clients,
                     ))
@@ -350,9 +371,10 @@ def run_one(
                 ))
             elif name == "placement":
                 run_suite(checks, shared(
-                    _with(scenario.run, known_failures={
-                        PLACEMENT_INTEGER_CASE: PLACEMENT_INTEGER_BUG
-                    }),
+                    _with(scenario.run, known_failures=None
+                          if _contains(PLACEMENT_INTEGER_FIX) else {
+                              PLACEMENT_INTEGER_CASE: PLACEMENT_INTEGER_BUG
+                          }),
                     platform, checks,
                 ))
             else:
@@ -389,6 +411,10 @@ def run_one(
 def main(argv: list[str]) -> int:
     golden, bin_dir, out, *names = argv
     failed = 0
+    # the commit the binaries were built from, which build-ref.sh writes
+    commit_file = Path(bin_dir) / "commit"
+    if commit_file.exists() and not os.environ.get("KOMOREBI_E2E_COMMIT"):
+        os.environ["KOMOREBI_E2E_COMMIT"] = commit_file.read_text().strip()
     state = None
     if os.environ.get("KOMOREBI_E2E_STATE"):
         state = ensure(Path(golden), Path(os.environ["KOMOREBI_E2E_STATE"]))