Use onig from github

[cakebaker]

This PR is a new attempt to get onig working with GCC 15 after the approach with setting CFLAGS='-std=gnu17' (#7944) failed. It also adds some entries to deny.toml to fix warnings from cargo-deny.

[tertsdiepraam]

At what point do we just drop it? It wouldn't be compatible but it seems to be more work than it's worth?

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)

[drinkcat]

Hopefully a new release is coming soon... rust-onig/rust-onig#195

[frendsick]

At what point do we just drop it? It wouldn't be compatible but it seems to be more work than it's worth?

The onig is only used for expr to support grep's regex syntax flavor. It is decently close to BRE syntax, but does not exactly match the needs of expr. We still need to transpile the user input to make it compatible with GNU expr, as there are still multiple ignored test_bre* tests.

It would be possible to drop onig by writing a transpiler from the BRE syntax to Rust's regex. It requires more code than with onig, but at least the resulting regex would be compatible with modern regex syntax and support modern features. It could also be easy enough to maintain, as people should be more accustomed to modern regex syntax and there are good tools for debugging modern regex syntaxes, like regex101. I do not know any such tools for BRE syntax.

[frendsick]

If the BRE --> Rust regex transpiler sounds like a decent idea, I could draft one and see how it would feel.

[drinkcat]

Hopefully a new release is coming soon... rust-onig/rust-onig#195

We could use #7973 + cargo update onig_sys. Or just wait for 6.5.1.

[cakebaker]

Closing this PR in favor of #7976