pullbundle: add a config option for the cache directory

pullbundle: add an output about the time spent slicing the set This will be useful to monitor overall performance.

pullbundle: add extension documentation

pullbundle: add an extra test showing how cache are reusable We issue a single final pull, most of its item are reusable.

pullbundle: add caching logic We now only generate a bundle once (and store it to disk). If we need it again, we use it directly from disk.

pullbundle: slice pull into multiple ranges We subdivide the set of missing revisions into multiple "range" using the "stable range" data structure. This slicing aims at maximizing the capability of the resulting ranges.

pullbundle: initial commit Right now, we do not do any slicing, but we install the wrapping and the tests.

test: update output to make streamv2 capabilities CORE-TEST-OUTPUT-UPDATE: 4bd6e444c76f

branching: merge with stable

topic: respect preexisting 'topic' value on workingcommitctx Mercurial's core changeset: 6c8ceebce309 revealed an issue. If the creator of a workingcommitctx explicitly assigned a 'topic', it was silently overridden by the current active on. This break import of patch with topic information. We now respect preexisting topic information.