rust-index: add checks that `__contains__` is synchronized

rust-index: using the Rust index in nodemap updating methods

rust-index: implementation of __getitem__ Although the removed panic tends to prove if the full test suite did pass that the case when the input is a node id does not happen, it is best not to remove it right now. Raising IndexError is crucial for iteration on the index to stop, given the default CPython sequence iterator, see for instance https://github.com/zpoint/CPython-Internals/blobs/master/BasicObject/iter/iter.md This was spotted by `test-rust-ancestors.py`, which does simple interations on indexes (as preflight checks). In `revlog.c`, `index_getitem` defaults to `index_get` when called on revision numbers, which does raise `IndexError` with the same message as the one we are introducing here.

rust-index: optim note for post-scaffolding removal

rust-index: check that the entry bytes are the same in both indexes This is a temporary measure to show that both the Rust and C indexes are kept in sync. Comes with some related documentation precisions. For comparison of error cases, see `index_entry_binary()` in `revlog.c`.

rust-index: return variables systematic naming convention To help knowing at a glance when a method is ready, making us more comofortable when we are close to the final removal of scaffolding, we introduce the systematic variable names `rust_res` and `c_res`. The goal of this series is to always return the formet. We take again the case of `pack_header` as example. Our personal opinion is to usually avoid such poor semantics as `res`, but usually accept it when it close to the actual return, which will be the case in most methods of this series. Also, the name can simply be dropped when we remove the scaffolding. To follow on the example, the body of `pack_header()` should become this in the final version: ``` let index = self.index(py).borrow(); let packed = index.pack_header(args.get_item(py, 0).extract(py)?); Ok(PyBytes::new(py, &packed).into_object()); ``` in these cases it is close to the actual return and will be removed at the end entirely.

rust-index: results comparison helper with details This is a bit simpler to call and has the advantage of systematically log the encountered deviation. To avoid committing dead code, we apply it to the `pack_header` method, that was already returning the Rust result.

rust-index: helper for revision not in index not involving nodemap This is a good match for exceptions raised from the C implementation, when it is not about a nodemap inconsistency.

rust-index: renamed nodemap error function for rev not in index The function name was misleading, as the error wording mentions the nodemap, hence would not be appropriate for missing revisions not related to a nodemap lookup.

rust-index: add `pack_header` support

rust-index: support cache clearing I'm not 100% sure how useful it is outside of perf, but it's still worth implementing.

rust-index: check rindex and cindex return the same get_rev This is a temporary safeguard while we synchronize both indexes.

rust-index: synchronize remove to Rust index Future steps will bring the two indexes further together until we can rip the C index entirely when running Rust code.

rust-index: remove `__setitem__` method from the mixed index This is not defined on the Python or C one, and isn't used anywhere.

rust-index: check equality between rust and cindex for `__len__`

rust-index: synchronize append method We now append to the Rust index just as we do to the C index. Future steps will bring the two indexes further together until we can rip the C index entirely when running Rust code.

rust-revlog: teach the revlog opening code to read the repo options This will become necessary as we start writing revlog data from Rust.

rust-index: pass data down to the Rust index This will allow us to start keeping the Rust index synchronized with the cindex as we gradually implement more and more methods in Rust. This will eventually be removed.

rust-index: add append method This is the first time the Rust index has any notion of mutability. This will be used in a future patch from Python, to start synchronizing the Rust index and the C index.

rust-index: add an abstraction to support bytes added at runtimes In order to support appending data to the Rust index, we need to abstract data access away from the immutable (on-disk) bytes, to seemlessly fetch either from the preexisting data or from the newly added data.

rust-mixed-index: move the mmap keepalive into a function The same code will be used for keeping the new index mmap around.

rust-mixed-index: rename variable to make the next change clearer We're going to add another mmap reference holder, so let's rename this one first.

rust: fix cargo doc for hg-cpython

branching: merge with default We merge with the current children of the bad merge (37b52b938579)

branching: merge with stable This recreates `37b52b938579` right as a `hg branch --rev 5b186ba40001` screwed up the content.

changelog: disallow delayed write on inline changesets Since this will never happens, we can make the situation invalid and to stop to handling the associated the case. This simplify the random access file reading too.

changelog: never inline changelog The test suite mostly use small repositories, that implies that most changelog in the tests are inlined. As a result, non-inlined changelog are quite poorly tested. Since non-inline changelog are most common case for serious repositories, this lack of testing is a significant problem that results in high profile issue like the one recently fixed by 66417f55ea33 and 849745d7da89. Inlining the changelog does not bring much to the table, the number of total file saved is negligible, and the changelog will be read by most operation anyway. So this changeset is make it so we never inline the changelog, and de-inline the one that are still inlined whenever we touch them. By doing that, we remove the "dual code path" situation for writing new entry to the changelog and move to a "single code path" situation. Having a single code path simplify the code and make sure it is covered by test (if test cover that situation obviously) This impact all tests that care about the number of file and the exchange size, but there is nothing too complicated in them just a lot of churn. The churn is made "worse" by the fact rust will use the persistent nodemap on any changelog now. Which is overall a win as it means testing the persistent nodemap more and having less special cases. In short, having inline changelog is mostly useless and an endless source of pain. We get rid of it.

test-transaction-safety: glog out irrelevant flag The test is focussing on the inline flag, so we glob out the other to highlight that fact and prevent noise in the future.