revlog: recommit 49fd21f32695 with a fix for issue6528 `filelog.size` currently special cases two forms of metadata encoding: - copy data via the parent order as flag bit - censor data by peaking into the raw delta All other forms of metadata encoding including the empty metadata block are mishandled. In `basefilectx.cmp` the empty metadata block is explicitly checked to compensate for this. Restore 49fd21f32695, but disable it for filelog, so that the original flag bit use contines to work. Document all this mess for now in preparation of a proper rework. Differential Revision: https://phab.mercurial-scm.org/D11203

merge-lists: make it possible to specify pattern to match The `merge-lists` tool doesn't know anything about Python other than its regex that attempts to match import lines. Let's make it possible to pass in a custom regex so it's easy to use the tool for e.g. C/C++ `#include` lines or Rust `use` lines (given the limited). Differential Revision: https://phab.mercurial-scm.org/D12392