* fix: bound clone batches by output size, not artifact count (#88, #92)

The xfer server paginated a clone by a fixed 200-artifact count. A count cannot adapt to artifact size: 200 control artifacts and 200 large blobs produce wildly different messages, and neither corresponds to what the transport can carry. It capped a libfossil-served clone near 20,000 artifacts against our own MaxRounds=100 client, and left the response size unbounded in the other direction -- serving libfossil's own repository produced a single 44.9 MB round.

emitCloneBatch now accumulates the wire bytes it emits and stops once they reach DefaultCloneBatchBytes, mirroring canonical's `while( mxSend > blob_size(pOut) )`: the budget is tested before each artifact and the artifact that crosses it is still sent whole, which is what keeps the cursor advancing when one artifact exceeds the entire budget. The card header is charged alongside the payload so a repository of zero-length artifacts still paginates. Section 8.2 leaves the bound to the server ("clients MUST NOT infer count or size from range").

The budget is 16 MB rather than canonical's 5,000,000 max-download because this clone path emits fully expanded artifacts where canonical retransmits stored compressed form (Section 7.2) -- 80x to 220x the bytes on real repositories. Measured on libfossil's own repository (17,218 artifacts): 87 rounds and a 44.9 MB worst-case response before, 65 rounds and 24.7 MB after. Canonical's constant applied to expanded bytes would have needed 184 rounds, breaking clones that work today.

Adds the interop half: a canonical fossil 2.28 client cloning a generated corpus from `repo serve`, sized past the pagination boundary, checked for round-trip count, artifact parity with the source, and `fossil test-integrity`. The many-small-artifacts case is what discriminates the two bounds -- 2,056 artifacts clone in 3 round-trips under the size bound and 23 under the count bound. Corpus size is a parameter since the interesting behaviour is at the boundary. A missing fossil binary skips, or fails under REQUIRE_FOSSIL_BIN=1.

* review: state the ceiling honestly, fix the overhead comment

The size bound replaces an artifact-count ceiling with an expanded-bytes ceiling. It is a better ceiling and it beats the count bound on every corpus measured, but fossil- and sqlite-sized repositories still cannot be cloned from a libfossil server within MaxRounds. Record the full three-repository round table on DefaultCloneBatchBytes and say outright that only Section 7.2 removes the ceiling rather than moving it.

State the memory property as budget plus the largest artifact, not as a 24.7 MB ceiling. The crossing artifact is sent whole, so a repository holding one 2 GB artifact still emits a 2 GB round, and concurrent clones multiply it. 45 MB -> 25 MB is a large reduction of a pre-existing unbounded allocation, not a cap.

cloneCardOverheadBytes claimed to cover the hash and then len(uuid) was added on top, double-charging it. Drop the addend; 96 over-approximates the ~58-byte framing on its own and the slack absorbs the uncharged PrivateCard.

Also: smallBatch sets a one-byte budget rather than a batch size of one, so correct the comments that still describe the old knob; drop the post-loop multi-batch > single-batch check, which passes under both bounds and so discriminates nothing; and make serveRepo report a server that exited early instead of signalling into an uninstalled handler, where SIGINT's default action would kill the test binary outright.

* test: count clone batches on the server, not round-trips on the client

CI (fossil 2.23) and this machine (2.28) disagreed on an identical server: the multi-batch clone reported 1 round-trip against CI and 9 locally. The clone was correct in both cases.

fossil prints "Round-trips: N" carriage-return separated, once per round. 2.28 guards those prints behind bOutIsTty and adds a single final line for non-TTY output, so a captured clone yields exactly one occurrence holding the total. 2.23 has no such guard and emits every round into the capture, so the regex's first match was always 1 no matter how many rounds ran. Verified by cloning one repository from a real fossil server with both binaries: 2.28 prints "Round-trips:" once, 2.23 four times, first line 1 and last line 2.

So the assertion silently meant different things on different clients, and many-small-artifacts -- the only case that discriminates a size bound from a count bound -- was passing under 2.23 for the wrong reason, inert rather than green.

Count the clone batches the server emits instead. That is the property under test, it cannot be distorted by client-side reporting, and it is sharper: many-small-artifacts is 2 batches under the size bound against 22 under a reinstated count bound, where the round-trip numbers were 3 against 23.

This serves via sync.ServeHTTP directly so the handler can be wrapped. RepoServeCmd.Run is a five-line wrapper around the same call and TestRepoServeCmdCanonicalFossilClone still drives the command end to end. It also drops these subtests' use of the process-wide SIGINT. check-in: 37271d3f68 user: [email protected] tags: trunk