stream-clone: add a explicit test for format change during stream clone They are different kind of requirements, the one which impact the data storage and are relevant to the files being streamed and the one which does not. For example some requirements are only relevant to the working copy, like sparse, or dirstate-v2. Since they are irrelevant to the content being streamed, they do not prevent the receiving side to use streaming clone and mercurial skip adverting them over the wire and, ideally, within the bundle. In addition, this let the client decide to use whichever format it desire for the part that does not affect the store itself. So the configuration related to these format are used as normal when doing a streaming clone. In practice, the feature was not really tested and is badly broken with bundle-2, since the requirements are not filtered out from the stream bundle. So we start with adding simple tests as a good base before the fix and adjust the feature. Differential Revision: https://phab.mercurial-scm.org/D12029