dirstate: add a function to update tracking status while "moving" parents The `scmutil.dirstateparent` is moving the dirstate parent without touching the working copy. It is used by history-rewriting operations like amending of folding. The function was directly doing the "low level" computation and dirstate change. All that logic belong to the dirstate and should be moved there. For this purpose we introduce a new function that does just that and use it. Differential Revision: https://phab.mercurial-scm.org/D11012

dirstate: introduce an internal `_drop` method We want to split current user of `dirstate.drop` between `hg rm`-like cases and update of the dirstate coming from update/merge. To do this we will introduce new API. The first step is to introduces an internal function that these new API migh use (or not use) to distinct between the migrated users and the others. Differential Revision: https://phab.mercurial-scm.org/D11023

dirstate: introduce an internal `_remove` method We want to split current user of `dirstate.remove` between `hg rm`-like cases and update of the dirstate coming from update/merge. To do this we will introduce new API. The first step is to introduces an internal function that these new API migh use (or not use) to distinct between the migrated users and the others. Differential Revision: https://phab.mercurial-scm.org/D11011

dirstate: introduce an internal `_add` method We want to split current user of `dirstate.add` between `hg add`-like cases and update of the dirstate coming from update/merge. To do this we will introduce new API. The first step is to introduces an internal function that these new API migh use (or not use) to distinct between the migrated users and the others. Differential Revision: https://phab.mercurial-scm.org/D11010

run-tests: rely on an actual executable in PATH instead of alias for `hg` The alias approach is poorly inherited by other process that the test might spawn. To solve this we use the same approach as for `python`/`python3` we write an executable file explicitly. Doing this fixes `which hg` invocation that now returns the same location as `hg`. Using chg server side has some minor effect on some stdout/stderr ordering when using `chg` as the server too. Differential Revision: https://phab.mercurial-scm.org/D11053

tests: blacklist a handful of test with `rhg` or `chg` The use of `alias` to enforce `chg` and `rhg` means we are actually using a mix of `rhg`/`chg` and `hg` when calling `hg` in the test. Fixing this breaks various tests. This would be a large detour to fix that. I am disabling them for now with an appropriate comment. We would hopefully get back to them by the 5.8 release. Differential Revision: https://phab.mercurial-scm.org/D11052

run-tests: use more explicit signaling for `chg` Using a dedicated variable is clearer and less fragile. It cannot hurt. Differential Revision: https://phab.mercurial-scm.org/D11051