dirstate-tree: Remove DirstateMap::iter_node_data_mut In an upcoming changeset we want DirstateMap to be able to work directly with nodes in their "on disk" representation, without always allocating corresponding in-memory data structures. Nodes would have two possible representations: one immutable "on disk" refering to the bytes buffer of the contents of the .hg/dirstate file, and one mutable with HashMap like the curren data structure. These nodes would have copy-on-write semantics: when an immutable node would need to be mutated, instead we allocate new mutable node for it and its ancestors. A mutable iterator of the entire tree would still be possible, but it would become much more expensive since we’d need to allocate mutable nodes for everything. Instead, remove this iterator. It was only used to clear ambiguous mtimes while serializing the `DirstateMap`. Instead clearing and serialization are now two separate passes. Clearing first uses an immutable iterator to collect the paths of nodes that need to be cleared, then accesses only those nodes mutably. Differential Revision: https://phab.mercurial-scm.org/D10744

merge with stable

revlog: close the index file handle after the data one This make sure the data file is flushed before the index. preventing the index to reference unflushed data. Differential Revision: https://phab.mercurial-scm.org/D10776

revlog: simplify the try nesting in the `_writing` context Lets use a single try, with conditional cleanup. This make is easier to add a file handle dedicated to sidedata. Differential Revision: https://phab.mercurial-scm.org/D10775