Looks good to me.

LGTM

More typos

Another typo

some more typos

For reference, same article is posted at

Although this is already landed, I had a 0.20.12 node synced to the non-upgraded chain, so I took the opportunity to test this Diff, and it behaved as expected.

Checked out the new DNS seeder, seems good to me.

Just the list numbering fix, otherwise seems good to me.

Just a small comment/quibble: The name of the Diff seems misleading to me, it makes it sound like it's just adding a test, not changing behavior. But isn't it actually changing how the code work also?

The Diff title seems to have a spurious "the":

Looks good to me.

Nit: Filename "abc-phonos-disconnectpool.py" should change phonos -> phonon

@tobias_ruck Could you change the name to OP_REVERSEBYTES in the Diff title?

In D4871#117783, @tobias_ruck wrote:

Renamed to OP_ENDIAN_REVERSE, reasons can be found in the PR:

In a previous proposal, this opcode has been named OP_REVERSE. After that, it has been renamed to OP_BSWAP, as that is a more technically accurate term, which is commonly used for reversing the byteorder of integers [14] [15]. However, after some more consideration, it has been renamed to OP_ENDIAN_REVERSE following Boost‘s nomenclature [16]. This is because OP_BSWAP is lexically very similar to the already existing OP_SWAP and would make Script harder to read. Also, while the technical term for the instruction is indeed bswap, it isn‘t well known for developers of higher level languages and could thus spark confusion that would be avoided by using the name OP_ENDIAN_REVERSE, which is more self-descriptive.

Also added tests for unexecuted branches, clarified tests for not yet activated case.

Merged D4859 into this diff.

In D4871#117550, @tobias_ruck wrote:

I‘ve left the SCRIPT_ENABLE_OP_BSWAP flag at bit 22, this should be coordinated with @markblundeberg

@tobias_ruck something is mangled with this Diff. Did you amend the previous Git commit? (You should amend) Or just add another commit?

@Fabien Should Cmake build instructions be added to the secp256k1 readme at /src/secp256k1/README.md ?
It currently has the autotools build instructions

Since it's coming from a different repo than most ABC backports, the Diff summary should mention what repo these backports are coming from and/or link to them

Fix typo

Add link directing contributors to Bitcoin ABC Phabricator repo
Re-add Travis link, now that Travis is enabled for the repo

Add a bit more explanation of how the repository is maintained, so that people can understand what's going on.
Re-add "Use at your own risk" disclaimer as recommended by @Fabien
Add link and mention that this is the Bitcoin Cash variant of the Schnorr algorithm.

@markblundeberg It may also be good to add some Schnorr information to the "Implementation Details" portion, and maybe a link to the BCH Schnorr spec on bitcoincash.org. Please let me know if you have any suggestions.

In D4673#113173, @markblundeberg wrote:

Also, what is NULLDUMMY? No such flag exists. ;-)

@markblundeberg you say " It is currently the only additive flag so it's the only one with weird behaviour like this."