When sync-typeshed fails to apply CP allow manual user merges (#15591)

If misc/sync-typeshed.py fails to apply a cherry pick, it just fails.
Let's try to give the user a chance to manually merge the CP and
continue with the script.
This should block for user input only in cases where stdin is a tty. So
automation should continue failing. (but the only way to test is by
running it)

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Alex Waygood <[email protected]>

misc/sync-typeshed.py

@@ -185,7 +185,21 @@ def main() -> None:
         "9f3bbbeb1",  # ParamSpec for functools.wraps
     ]
     for commit in commits_to_cherry_pick:
-        subprocess.run(["git", "cherry-pick", commit], check=True)
+        try:
+            subprocess.run(["git", "cherry-pick", commit], check=True)
+        except subprocess.CalledProcessError:
+            if not sys.__stdin__.isatty():
+                # We're in an automated context
+                raise
+
+            # Allow the option to merge manually
+            print(
+                f"Commit {commit} failed to cherry pick."
+                " In a separate shell, please manually merge and continue cherry pick."
+            )
+            rsp = input("Did you finish the cherry pick? [y/N]: ")
+            if rsp.lower() not in {"y", "yes"}:
+                raise
         print(f"Cherry-picked {commit}.")
 
     if args.make_pr: