getbundle: add support for 'bookmarks' boolean argument This new argument requests a 'bookmarks' part from the server. It is meant to be used instead of the "listkeys" request.

bundle2: support a 'records' mode for the 'bookmarks' part In this mode, the bookmarks changes are record in the 'bundleoperation' records instead of inflicted to the repository. This is necessary to use the part when pulling.

bundle2: add a 'modes' dictionary to the bundle operation This new attribute allows the codes requesting an unbundling to pass important information to individual part handlers. The current target use case is to allow for receiving 'bookmarks' part without directly updating local repository, but just recording the received data instead. This is necessary for pull where the remote bookmarks are processed locally. I expect the concept to be beneficial to other parts in the future. To clarify the bookmark behavior on pull, the remote bookmark value are not just taken -as-is- into the local repository. There is an extra step to detect bookmark divergence. The remote bookmarks data are stored until this processing happens.

bookmark: use the 'bookmarks' bundle2 part to push bookmark update (issue5165) We use the new binary parts we introduced earlier to exchange bookmark. The payload is a bit more compact since we use binary and the length of bookmarks is no longer constrained to 255. .. fix:: Issue 5165 Bookmark, whose name is longer than 255, can again be exchanged again between 4.4+ client and servers.

bookmark: introduce in advance a variant of the exchange test We are about to introduce a new way to push bookmark to server. We introduce the test variant before actually updating the exchange to help the output changes to stand out when it happens.

push: move bundle2-pushkey based bookmarks exchange in its own function We are about to introduce an alternative way to push bookmark over bundle2.

bookmark: add pushkey hook compatiblity to the bundle2 part Currently, pushing a bookmark update triggers a pushkey hooks. It is likely that users in the wild use such hooks to control bookmark movement. Using a non push-key mechanism to exchange bookmark means these hooks are no longer called, possibly breaking existing users setup. So we add explicit call to the pushkey hooks in the handling of the bundle2 part. This behavior can be disabled with a new config knob: 'server.bookmarks-pushkey-compat'.

bookmark: introduce a 'bookmarks' part This part can carry and apply bookmarks information. We start with adding the core behavior of the part. In its current form, the part is only suitable for push since it plain update the bookmark without consideration for the local state. Support of the behavior needed for pulling will be added in later changesets.

push: include a 'check:bookmarks' part when possible Before updating the actual bookmark update, we can start with updating the way we check for push race. Checking bookmarks state earlier is useful even if we still use pushkey. Aborting before the changegroup is added can save a lot of time.

bookmark: add a 'check:bookmarks' bundle2 part This part checks that bookmarks are still at the node they are expected to be. This allows a pushing client to detect push race where the repository was updated between the time it discovered the server state and the time it managed to finish its push. Such checking already exists when pushing bookmark through pushkey. This new part can be inserted at the beginning of the bundle, triggering abort earlier. In addition, we would like to move away from pushey to push bookmark. A step useful to solve issue5165.