relnotes: add release notes for 6.1.2

docs: use proper rst markup for preformatted blocks The multiple lines were re-flowed to a single line, both in man page and html.

test-dirstate: print something when the check is skipped This makes a programming error obvious in cases when it should not be skipped Differential Revision: https://phab.mercurial-scm.org/D12602

test-dirstate: fix detection of Rust environment variable The Rust path never actually worked. This change also improves clarity of the comment. The next change will ensure we print something when this check fails. Differential Revision: https://phab.mercurial-scm.org/D12601

rust-dirstate-v2: fix the unused bytes counter when rewriting the dirstate As per the previous patch, the counter was incorrectly carried over from the old docket when it should be reset for a complete rewrite. Differential Revision: https://phab.mercurial-scm.org/D12594

rust-dirstate-v2: show `unused_bytes` counter is not reset on total rewrite This was picked up by @aalekseyev when doing unrelated debugging. The Rust implementation was never resetting this counter, so a brand new file would carry over the old counter. As I write this, my counter is a supposed 7389089 unused bytes for a total of 170978 bytes in the data file. Feel free to post your own high score. Differential Revision: https://phab.mercurial-scm.org/D12593

test-dirstate: use new `--docket` flag to get the data uuid This is more robust. Differential Revision: https://phab.mercurial-scm.org/D12592

debugcommands: remove `debugdirstateignorepatternhash` This is replaced by the more complete `--docket` option to `debugstate`. Differential Revision: https://phab.mercurial-scm.org/D12591