requirements: move the comment about manifestv2 in the module This is about requirements, so lets put it into the requirements module. We are about to remove code it was previously attached too. Differential Revision: https://phab.mercurial-scm.org/D12033

stream-clone: add a explicit set list requirements relevant to stream clone This set explicitly lists all the requirements that "stream clone" will preserve. Any other one will not be preserved. The role of listing the relevant one was previously filled by `repo.supportedformat`, but it seems clearer to use that such global and explicit set. The `repo.supportedformat` attribute will be cleaned up in a later changeset The true meaning of `repo.supportedformat` vs `repo._basesupported` was lost over time so, the content is currently bad. For example, `dirstate-v2` is currently considered relevant to the stream clone, or internal phase is missing. We kept the same content in this changeset and we will fix them later. Differential Revision: https://phab.mercurial-scm.org/D12032

stream-clone: filter possible missing requirements using all supported one The `supportedformat` requirements is missing some important requirements and it seems better to filter out with all requirements we know, not just an "arbitrary" subset. This is especially relevant as we about to phase out the `supportedformat` class attribute. (a backport of this change to stable should be sent soon). Differential Revision: https://phab.mercurial-scm.org/D12031

requirements: move "bookmark in store" requirements in the right module There seems to be no reasons to not have it with the others. Differential Revision: https://phab.mercurial-scm.org/D12030

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

stream-clone: factor computation of requirement of a stream clone This gather code duplicated in multiple place and will make it easier to modify it safely in the future. Differential Revision: https://phab.mercurial-scm.org/D12028