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.
test/framework/src/main/java/org/elasticsearch/snapshots/AbstractSnapshotIntegTestCase.java
}
    protected void deleteRepository(String repoName) {
        assertAcked(client().admin().cluster().prepareDeleteRepository(repoName));
    }
    public static Settings.Builder randomRepositorySettings() {
        final Settings.Builder settings = Settings.builder();
        settings.put("location", randomRepoPath()).put("compress", randomBoolean());
        if (rarely()) {
            settings.put("chunk_size", randomIntBetween(100, 1000), ByteSizeUnit.BYTES);
        }
        if (randomBoolean()) {
            settings.put(BlobStoreRepository.USE_FOR_PEER_RECOVERY_SETTING.getKey(), randomBoolean());
        }
        return settings;
    }
    protected static Settings.Builder indexSettingsNoReplicas(int shards) {
        return Settings.builder().put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, shards).put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0);
    }
    /**
     * Randomly write an empty snapshot of an older version to an empty repository to simulate an older repository metadata format.
     */
    protected void maybeInitWithOldSnapshotVersion(String repoName, Path repoPath) throws Exception {
        if (randomBoolean() && randomBoolean()) {
            initWithSnapshotVersion(repoName, repoPath, VersionUtils.randomIndexCompatibleVersion(random()));
        }
    }
    /**
     * Workaround to simulate BwC situation: taking a snapshot without indices here so that we don't create any new version shard
     * generations (the existence of which would short-circuit checks for the repo containing old version snapshots)
     */