test-flagprocessor: add tests about bundlerepo This shows flag processor is broken with a bundle repo. The test creates non-liner history to exercise code path where the deltaparent cannot be reused.

test-flagprocessor: use changegroup3 in bundle2 This will force "hg bundle" to use changegroup3 in the test. It is important since only changegroup3 preserves revlog flags.

bundle: allow bundle command to use changegroup3 in tests Since bundle2 writes changegroup version, we can just reuse the bundle2 format for changegroup3. This won't enable the bundle command to write changegroup3 in the wild, since exchange.parsebundlespec only returns changegroup2. It unlocks tests to override exchange.parsebundlespec and get "hg bundle" write changegroup3.