Rollup merge of #143630 - jieyouxu:drop-suggest, r=Mark-Simulacrum

Drop `./x suggest`

This PR removes the current `./x suggest` implementation (rust-lang/rust#109933, rust-lang/rust#106249) and associated docs for several reasons:

1. Primarily, `./x suggest` is another "flow" in bootstrap that incurs extra complexity and more invariants that bootstrap has to maintain. This causes more friction when trying to investigate and fix staging problems. As far as I know, this flow has not been actively maintained in quite a while, and I'm not aware of interest in maintaining it. Bootstrap really could use less implementation complexity with a very limited maintenance bandwidth.
2. The current `./x suggest` implementation "bypasses" the usual stage defaults for the various check/build/test/etc. flows, and it's not really possible to have a stage default because `./x suggest --run` produces a *sequence* of suggestions like [`./x check`, `./x test library/std`, ..] and then tries to run all of them in sequence, based on which files are modified.
3. We've not seen a lot of interest both in using it or extending static/dynamic test suggestions. Last extensions were rust-lang/rust#117961 and rust-lang/rust#120763. I'm not convinced the extra implementation complexity is worth it. This was discussed in:
    - [#t-infra/bootstrap > Dropping the current `./x suggest` flow implementation](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Dropping.20the.20current.20.60.2E.2Fx.20suggest.60.20flow.20implementation/with/527456699)
    - [#t-compiler > Dropping current `./x suggest` implementation](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Dropping.20current.20.60.2E.2Fx.20suggest.60.20implementation/with/527528696)

Closes rust-lang/rust#109933 (the current implementation is being removed).
Closes rust-lang/rust#143569 (by removing `./x suggest` altogether).

Author: samueltardieu

src/SUMMARY.md

@@ -35,7 +35,6 @@
         - [Cranelift codegen backend](./tests/codegen-backend-tests/cg_clif.md)
         - [GCC codegen backend](./tests/codegen-backend-tests/cg_gcc.md)
     - [Performance testing](./tests/perf.md)
-    - [Suggest tests tool](./tests/suggest-tests.md)
     - [Misc info](./tests/misc.md)
 - [Debugging the compiler](./compiler-debugging.md)
     - [Using the tracing/logging instrumentation](./tracing.md)

src/building/quickstart.md

@@ -61,9 +61,6 @@ and check the output.
 Use `--bless` if you've made a change and want to update the `.stderr` files
 with the new output.
 
-> `./x suggest` can also be helpful for suggesting which tests to run after a
-> change.
-
 Congrats, you are now ready to make a change to the compiler! If you have more
 questions, [the full chapter](./how-to-build-and-run.md) might contain the
 answers, and if it doesn't, feel free to ask for help on

src/building/suggested.md

@@ -270,23 +270,6 @@ run the tests at some later time. You can then use `git bisect` to track down
 is that you are left with a fairly fine-grained set of commits at the end, all
 of which build and pass tests. This often helps reviewing.
 
-## `x suggest`
-
-The `x suggest` subcommand suggests (and runs) a subset of the extensive
-`rust-lang/rust` tests based on files you have changed. This is especially
-useful for new contributors who have not mastered the arcane `x` flags yet and
-more experienced contributors as a shorthand for reducing mental effort. In all
-cases it is useful not to run the full tests (which can take on the order of
-tens of minutes) and just run a subset which are relevant to your changes. For
-example, running `tidy` and `linkchecker` is useful when editing Markdown files,
-whereas UI tests are much less likely to be helpful. While `x suggest` is a
-useful tool, it does not guarantee perfect coverage (just as PR CI isn't a
-substitute for bors). See the [dedicated chapter](../tests/suggest-tests.md) for
-more information and contribution instructions.
-
-Please note that `x suggest` is in a beta state currently and the tests that it
-will suggest are limited.
-
 ## Configuring `rustup` to use nightly
 
 Some parts of the bootstrap process uses pinned, nightly versions of tools like