merge stable in default

dirstate: revert change to Rust binding The Rust binding uses its own class and is not derived from the regular implementation. As such, it didn't get _nodelen. Differential Revision: https://phab.mercurial-scm.org/D8849

relnotes: copy "next" to "5.5" and clear "next" The same procedure as every year^Wcycle. Differential Revision: https://phab.mercurial-scm.org/D8839

commitctx: extract all the file preparation logic in a new function Before we actually start to create a new commit we have a large block of logic that do the necessary file and manifest commit and that determine which files are been affected by the commit (and how). This is a complex process on its own. It return a "simple" output that can be fed to the next step. The output itself is not that simple as we return a lot of individual items (files, added, removed, ...). My next step (and actual goal for this cleanup) will be to simplify the return by returning a richer object that will be more suited for the variation of data we want to store. After this changeset the `commitctx` is a collection of smaller function with limited scope. The largest one is still `_filecommit` without about 100 lines of code.

commitctx: gather more preparation code within the lock context This is a small change that exist mostly for clarification. I am about to move a large amount of code in its own function. having all that code next to each other will make the next changeset clearer.

commitctx: move a special case about files earlier Same logic as a changeset a bit earlier, the `writefilecopymeta` section is more a post processing details so we move the conditional about `files` value closer to the rest of the code computing `files` value.

commitctx: extract all the manual logic to process the files That branch of the if is significantly more complicated than the other two. Moving it to its own function make it simple to keep the scope limited and to read to the higher level function.

commitctx: treat `filesadded` more like `filesremoved` Accumulating the filename in a list will have a negligible cost and deal with the list of added files like the other ones will make is code cleaning simpler. The two variable with very close name is not great, but my plan is to split most of the code in a separated function which will make the "problem" go away by itself.

commitctx: move `writechangesetcopy` business at the end a code section This code is to handle a specific subcase so we move it a the end. This allow to gather the rest of the "core" code closer to the related logic.

commitctx: move copy meta config reading in a dedicated function The logic is non trivial, make it contained in a function is clearer. It also unlock easy re-use of that logic without having the pass the value around.