ci: normalize mtimes for eth2shuffle and genesiswrite fixtures

cl/utils/eth2shuffle reads spec/tests.csv at runtime and
execution/state/genesiswrite reads genesis_test.json at runtime.
Neither path was covered by git restore-mtime, so their mtimes varied
between CI runs and prevented Go test result caching for those packages.

Document the requirement: any test that reads a data file at runtime
outside a testdata/ directory must add it to the restore-mtime list.

Author: anacrolix

.github/actions/setup-erigon/action.yml

@@ -172,12 +172,16 @@ runs:
         #   execution/tests/test-corners/** - custom edge-case fixtures
         #   cl/spectest/**/data_*/** - consensus spec test data
         #   cl/transition/**/test_data/** - consensus transition test data
-        #   Extensions: .json .js .txt .ssz .ssz_snappy .yaml
+        #   cl/utils/eth2shuffle/spec/** - shuffle spec CSV (read at runtime)
+        #   execution/state/genesiswrite/*.json - genesis JSON (read at runtime)
+        #   Extensions: .json .js .txt .ssz .ssz_snappy .yaml .csv
         time git restore-mtime --no-directories -- \
           '**/testdata/**' \
           'execution/tests/test-corners/**' \
           'cl/spectest/**/data_*/**' \
-          'cl/transition/**/test_data/**'
+          'cl/transition/**/test_data/**' \
+          'cl/utils/eth2shuffle/spec/**' \
+          'execution/state/genesiswrite/*.json'
 
         # Submodules are all fixture data; set mtimes to HEAD commit time.
         git submodule foreach --quiet --recursive \

agents.md

@@ -75,3 +75,11 @@ Common lint categories and fixes:
 ## Workflows
 
 Make sure all scripts and shell code used from GitHub workflows is cross platform, for macOS, Windows and Linux.
+
+## Go Test Caching
+
+Go's test result cache keys on the mtime+size of every file read (via Go stdlib) during a test run. CI normalizes mtimes via `git restore-mtime` in `.github/actions/setup-erigon/action.yml` so that unchanged files get stable mtimes across runs.
+
+**When a test reads a data file at runtime** (via `os.Open`, `os.ReadFile`, `os.Stat`, etc.) that lives outside a `testdata/` directory, it must be added to the `git restore-mtime` pattern list in `setup-erigon/action.yml`. Otherwise that package's test results will never be cached in CI.
+
+Covered patterns already include `**/testdata/**`, `execution/tests/test-corners/**`, `cl/spectest/**/data_*/**`, `cl/transition/**/test_data/**`, `cl/utils/eth2shuffle/spec/**`, and `execution/state/genesiswrite/*.json`.