Today if we detect concurrent modification of a snapshot repository then we mark it with `CORRUPTED_REPO_GEN` which blocks further writes to try and prevent additional damage to its contents. You can remove the marker by calling the register-repository API again, but this API will discard no-op re-registrations without taking any action. You can work around this by unregistering the repository first (which may be impossible if it's still in use for searchable snapshots) or by re-registering it with some trivial setting change (which seems hacky).

We should not consider it a no-op re-registration if the repository is currently marked with `CORRUPTED_REPO_GEN`, because doing this re-registration will re-read the repo contents and clear the corruption marker and therefore is not a no-op.
server/src/internalClusterTest/java/org/elasticsearch/snapshots/ConcurrentSnapshotsIT.java
unblockNode(repoName, dataNode);
        assertSuccessful(blockedSnapshot);
        assertSuccessful(otherSnapshot);
    }
    public void testConcurrentRestoreDeleteAndClone() throws Exception {
        final String repository = "test-repo";
        createRepository(logger, repository, "fs");
        final int nbIndices = randomIntBetween(10, 20);
        for (int i = 0; i < nbIndices; i++) {
            final String index = "index-" + i;
            createIndexWithContent(index);
            final String snapshot = "snapshot-" + i;
            createSnapshot(repository, snapshot, List.of(index));
        }
        final List<ActionFuture<AcknowledgedResponse>> cloneFutures = new ArrayList<>();
        final List<ActionFuture<RestoreSnapshotResponse>> restoreFutures = new ArrayList<>();
        for (int i = 0; i < nbIndices; i++) {
            if (randomBoolean()) {
                restoreFutures.add(
                    client().admin()
                        .cluster()
                        .prepareRestoreSnapshot(repository, "snapshot-" + i)
                        .setIndices("index-" + i)
                        .setRenamePattern("(.+)")
                        .setRenameReplacement("$1-restored-" + i)
                        .setWaitForCompletion(true)
                        .execute()
                );
            } else {
                cloneFutures.add(