bundle2: detect and disallow a negative chunk size We have no usage planned for 2/3 of them and the support for the planned usecase is not here yet. So we raise a BundleValueError when encountered

bundle2: add an UnsupportedPartError We need the BundleValueError for format errors not related to part support. So we add a specific class for part-support errors.

bundle2: change header size and make them signed (new format) We are changing all integers that denote the size of a chunk to read to int32. There are two main motivations for that. First, we change everything to the same width (32 bits) to make it possible for a reasonably agnostic actor to forward a bundle2 without any extra processing. With this change, this could be achieved by just reading int32s and forwarding chunks of the size read. A bit a smartness would be logic to detect the end of stream but nothing too complicated. Second, we need some capacity to transmit special information during the bundle processing. For example we would like to be able to raise an exception while a part is being read if this exception happend while this part was generated. Having signed integer let us use negative numbers to trigger special events during the parsing of the bundle. The format is renamed for B2X to B2Y because this breaks binary compatibility. The B2X format support is dropped. It was experimental to allow this kind of things. All elements not directly related to the binary format remain flagged "b2x" because they are still compatible.

bundle2: extract processing of part into its own function This is code movement only. This will be useful to have it separated for reuse purposes. We plan to introduce a new feature to the bundle format that allow inserting a part in the middle of another part payload. This will be useful to transmit a exception raised during a part generation.

bundle2: add a test for exceptions raised during the generation process We would like exceptions raised during the generation process to be gracefully handled on the receiver side. We add a test for it. It shows that we are not doing it yet.

dagwalker: drop a useless intermediate variable The variable used to contain revs.set() but as the `.set()` has been removed it is now useless.

revset-node: speedup by a few hundred fold Instead of checking all elements of the subset against a single rev, just check if this rev is in the subset. The old way was inherited from when the subset was a list. Non surprise, this provide massive speedup. id("d82e2223f132") before) wall 0.008205 comb 0.000000 user 0.000000 sys 0.000000 (best of 302) after) wall 0.000069 comb 0.000000 user 0.000000 sys 0.000000 (best of 34518) revset #1: public() and id("d82e2223f132") before) wall 0.019763 comb 0.020000 user 0.020000 sys 0.000000 (best of 124) after) wall 0.000101 comb 0.000000 user 0.000000 sys 0.000000 (best of 20130)

revset-only: use `subset &` instead of filtering The & version is more likely to be optimised. only(.) before) wall 0.003216 comb 0.000000 user 0.000000 sys 0.000000 (best of 768) after) wall 0.001086 comb 0.000000 user 0.000000 sys 0.000000 (best of 2231) only(default, stable) before) wall 0.018469 comb 0.020000 user 0.020000 sys 0.000000 (best of 138) after) wall 0.015888 comb 0.010000 user 0.010000 sys 0.000000 (best of 156)

revset-_ancestor: use & instead of filter The & operation is more likely optimised. ::10 before) wall 0.028189 comb 0.030000 user 0.030000 sys 0.000000 (best of 100) after) wall 0.001050 comb 0.000000 user 0.000000 sys 0.000000 (best of 2326) ::tip before) wall 0.081132 comb 0.080000 user 0.080000 sys 0.000000 (best of 100) after) wall 0.055418 comb 0.050000 user 0.050000 sys 0.000000 (best of 100)

obsstore: record data as floating point in fm0 format For python struct module, "d" is double. But for python string formating, "d" is integer. We want to preserve the floating point nature of the data, so we store it in the metadata as floating point. We use "%r" to make sure we get as many significant digitis as necessary to restore the float to the exact same value on the other side. The fm1 is transmitting the information as float. The lack of this made fm1-stored markers not survive a round-trip to fm0 leading to duplicated markers (or two markers very alike).