changing-files: add a debug command display changed files The binary output from sidedata is useful to verify the underlying data do not get corrupted. However having a human readable version is much simpler for debuging the changed files data itself. So we add a debug command to dump this information and we use it in the tests. Differential Revision: https://phab.mercurial-scm.org/D9125

side-data: add a test to check sidedata upgrade We want to make sure that sidedata computed at commit time and during upgrade are the same. To do so, we upgrade the repository in `test-copies-chain-merge.t` since the file is checking all the special case that we need to catch. The sidedata content in both case should be the same. Differential Revision: https://phab.mercurial-scm.org/D9124

changing-files: split the changing files computation from encoding The side data encoding is already in its own function, now we move the changing files computation in it own function, it will receive more updates in the coming changesets. Differential Revision: https://phab.mercurial-scm.org/D9123

salvaged: record salvaged in ChangingFiles at commit time The new code is a simple but effective way to detect this information. We might be able to move it inside the various conditionnal above, but I want to focus on simplicity until we have a full working stack. It is worth noting that if we record the information in the ChangingFiles object, it is not persisted yet. This will comes with later changesets. Differential Revision: https://phab.mercurial-scm.org/D9120