shelve: find shelvedctx from bundle even if they are already in the repo We use the new "duplicates" node tracking to find the tip of the bundle even if it already exists in the repository. Such logic is not supposed to be needed in theory. If the shelve was made using internal-phase, we already know its node. Otherwise, the bundle content should have been stripped. However, handling it makes the shelve code more robust and provide a good example of "revduplicates" usage.

shelve: return the shelved node as part of bundle application It make sense to have the function in charge of unbundling the shelved revision also return the node of that revision (when the data is in the bundle). This will help us to handle unnatural state where the unshelved change already exists in the repository.

changelog: keep track of duplicated node in the transaction adding them The transaction is already tracking the new nodes. We now tracks the "duplicates" in the same location.

revlog: add a callback "tracking" duplicate node addition If a changegroup contains node already added to the repository, they will be skipped. Skipping them is the right behavior (we don't need to store things twice), but it can hide some information to the code doing the unbundle (eg: shelve looking for the tip of the bundle). The first step to improve this situation is to add a low level callback. We do not need this tracking on all revlog, so actual tracking will be added in the next changeset.