Merge cockroachdb#121915

121915: roachtest: add instructions for regenerating fixtures r=RaduBerinde a=RaduBerinde

Instructions are copied from the wiki.

Release note: None

Co-authored-by: Radu Berinde <radu@cockroachlabs.com>

pkg/cmd/roachtest/fixtures/README.md

@@ -0,0 +1,49 @@
+Roachtest fixtures
+----
+
+To regenerate these fixtures:
+
+1. Set `FIXTURE_VERSION` to the release or pre-release version you want to
+   generate fixtures for:
+```
+export FIXTURE_VERSION=v23.2.0-beta.1
+```
+
+Note that this version must exist in the
+[Releases](https://www.cockroachlabs.com/docs/releases) page.
+
+
+2. Make clean builds of CRDB, roachtest, workload, roachprod. Note that
+   roachtest needs to be run on amd64 (if you are using a Mac it's recommended to
+   use a gceworker).
+
+```
+./dev build cockroach roachprod workload roachtest
+## Clear out roachprod remnants, if any
+./bin/roachprod destroy local
+```
+
+3. Run roachtest against the `FIXTURE_VERSION` binary and generate the updated
+   fixtures:
+
+```
+./bin/roachtest run generate-fixtures --local --debug --cockroach ./cockroach tag:fixtures
+```
+
+This should produce an intentional failure, where you see something like:
+
+```
+--- FAIL: generate-fixtures (19.73s)
+test artifacts and logs in: artifacts/generate-fixtures/run_1
+versionupgrade.go:516,versionupgrade.go:189,versionupgrade.go:527,versionupgrade.go:102,acceptance.go:58,acceptance.go:95,test_runner.go:755: successfully created checkpoints; failing test on purpose.
+Invoke the following to move the archives to the right place and commit the
+result:
+for i in 1 2 3 4; do
+mkdir -p pkg/cmd/roachtest/fixtures/${i} && \
+mv artifacts/generate-fixtures/run_1/logs/${i}.unredacted/checkpoint-*.tgz \
+pkg/cmd/roachtest/fixtures/${i}/
+done
+```
+
+Follow the directions in the test failure output to copy the checkpoint files.
+Make sure the filenames are as expected and rename if necessary.