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)