bundle: do no check the changegroup version if no changegroup is included We don't need to check the compatibility of something we will not use. In practice this was getting in the was of `streamv2` bundles on a narrow repository as the 'cg.version=02' value was rejected by this checks.

perf-stream-consume: use the source repository config when applying This might contains critical configuration for the benchmark, like enabling of extensions like narrow.

unbundle: move most of the logic on cmdutil to help debug::unbundle reuse This make sure `hg debug::unbundle` focus on the core logic.

postincoming: move to cmdutil This looks like a good place for it to live.

postincoming: avoid computing branchhead if no report will be posted This otherwise defeat some of the branch v3 optimization.

streamclone: stop listing files for entries that have no volatile files This will save a lot of python related time. This significantly boost performance. The following number comes from a large private repository using perf::stream-locked-section: base-line: 35.04 seconds prev-change: 24.51 seconds (-30%) prev-change: 20.88 seconds (-40%) prev-change: 14.22 seconds (-60%) this-change: 11.58 seconds (-67% from baseline; -18% from prev)