hghave: fix the definition of `python3` to work on Windows Both py2 and py3 executables are named `python.exe`, and may or may not be on PATH. So use the dispatcher executable that comes with py3 to fetch the version of the latest py3 executable. This allows at least one relnotes test to run on Windows. Differential Revision: https://phab.mercurial-scm.org/D10694

util: avoid echoing the password to the console on Windows py3 (issue6446) The `getpass.getpass()` implementation on Windows first checks if `sys.stdin` and `sys.__stdin__` are the same object. It's not on py3 because the former is replaced in dispatch.py with something that doesn't normalize '\n' to '\r\n'. When they aren't the same object, it simply calls `sys.stdin.readline()` instead of the mscvrt functions that read the input characters before they are echoed. This simply copies the `getpass.win_getpass()` implementation without the stdin check, and byteifies around the edges. I'm not sure if there's a reasonable replacement for the check that we could implement. When echoing input into the hg command, the `ui.interactive()` check causes `ui.getpass()` to bail before getting here. If the proper config switches are used to bypass that and call this, the process stalls until '\n' is input into the console. So there could be a deadlock here when run by another command if the wrong config settings are applied. Differential Revision: https://phab.mercurial-scm.org/D10708

sidedata: enable sidedata computers to optionally rewrite flags Sidedata computers may want to influence the flags of the revision they touch. For example, the computer for changelog-based copytracing can add a flag to signify that this revision might affect copytracing, inversely removing said flag if the information is no longer applicable. See inline documentation in `storageutil` for more details. Differential Revision: https://phab.mercurial-scm.org/D10344

cg4: introduce protocol flag to signify the presence of sidedata We need a way of signaling whether the current revision has sidedata or not, and re-using the revision flags would waste potential revlog flags and mix two normally independent layers. In this change, we add a single byte at the start of the ch4 delta header to set potential protocol flags. We also reclaim the revlog flag for sidedata, since it is no longer used, in its place now lives the (also experimental) copytracing flag. When generating deltas, apply the `CG_FLAG_SIDEDATA` flag if there is sidedata. When applying the deltas, if said flag is present, the next chunk contains the sidedata. Differential Revision: https://phab.mercurial-scm.org/D10343

changegroup: don't limit cgv4 to revlogv2 repos To help the transition from revlogv1 to revlogv2, we need to be able to enable cgv4 for revlogv1 repos, so that revlogv2 clients can handle adding/removing sidedata over the wire. Differential Revision: https://phab.mercurial-scm.org/D10342

sidedata: gate sidedata functionality to revlogv2 in more places Since revlogv1 is not capable of storing sidedata, we prevent sidedata mechanisms around the revlog layer from doing anything. We however keep the ones that allow a revlogv1 repo to generate sidedata on-the-fly on a push, the pull case simply does not add the sidedata to the revlog. Differential Revision: https://phab.mercurial-scm.org/D10341