branching: merge with stable I need the fix to `generate-churning-bundle.py`.

generate-churning-bundle: fix script for python3 This script has apparently not run for a long time.

narrow: strip trailing `/` from manifest dir before matching it Commit 17a822d7943e broke some of our internal tests at Google because the `dir` variable contains a trailing slash since that commit. Let's restore the old behavior by stripping that trailing slash.

tests: demonstrate error when narrowing with `rootfilesin:` pattern This demonstrates a bug introduced in 17a822d7943e.

matchers: use correct method for finding index in vector The path matcher has an optimization for when all paths are `rootfilesin:`. This optimization exists in both Python and Rust. However, the Rust implementation currently has a bug that makes it fail in most cases. The bug is that it `rfind()` where it was clearly intended to use `rposition()`. This patch fixes that and adds a test.

dirstate: make the `transaction` argument of `setbranch` mandatory This is deprecated since 6.4. We should drop it now.

rust-clippy: apply some more trivial fixes All of these were hinted at by clippy and make the code simpler.

rust-clippy: simplify `match` to `if let` This was hinted at by clippy, and makes it more obvious that nothing is happening in the `None` case.

censor: accept multiple revision in a single call This is useful when dealing with corruption, as all the corrupted revision can be dealt with in one go.

censor: be more verbose about the other steps too If we informs the user about head checking, we should tell him when the other operation happens too. Otherwise the user can imagine to still be in the head checking part.