dirstate-v2: Enforce data size read from the docket file The data file may not be shorter than its size given by the docket. It may be longer, but additional data is ignored. Differential Revision: https://phab.mercurial-scm.org/D11089

dirstate-v2: Introduce a docket file .hg/dirstate now only contains some metadata to point to a separate data file named .hg/dirstate.{}.d with a random hexadecimal identifier. For now every update creates a new data file and removes the old one, but later we’ll (usually) append to an existing file. Separating into two files allows doing the "write to a temporary file then atomically rename into destination" dance with only a small docket file, without always rewriting a lot of data. Differential Revision: https://phab.mercurial-scm.org/D11088

dirstate: replace a dead conditional branch with an assert in `update_file` This is a case we never meet, so lets trim it away to simplify the code before more changes. Differential Revision: https://phab.mercurial-scm.org/D11128

dirstate-map: do not use `size` to gate copy dropping during remove_file This get us close to moving the block right above withing the DirstateItem object. Doing so will help us getting rid of magic constant at the dirstatemap level. Differential Revision: https://phab.mercurial-scm.org/D11127

dirstate: drop a duplicated assert This very case is checked in 3 line above that one. Differential Revision: https://phab.mercurial-scm.org/D11126

dirstate: drop duplicated check This is covered by the `@requires_parents_change` decorator that this function use. Differential Revision: https://phab.mercurial-scm.org/D11125

dirstate: add a `set_possibly_dirty` in `fakedirstatewritetime` Differential Revision: https://phab.mercurial-scm.org/D11122

dirstatemap: use `set_possibly_dirty` in `clearambiguoustimes` lets put this new method to use Differential Revision: https://phab.mercurial-scm.org/D11121

dirstate-item: use `set_possibly_dirty` in `pure.pack_dirstate` Lets make use of the new function. Differential Revision: https://phab.mercurial-scm.org/D11120

dirstate-item: add a `set_possibly_dirty` method See inline documentation for details. The pushes the AMBIGUOUS_TIME implementation further down the line within the DirstateItem only. When this cleanup is done we will be able to stop using this representation internally. Differential Revision: https://phab.mercurial-scm.org/D11119