Downstream impact from https://codereview.chromium.org/1693993002/

scripts/slave/recipes/perf/ct_top1k_perf.expected/CT_Top1k_slave2_failure.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "chromium.perf.fyi",
       "--builder",
       "Linux CT Top1k RR Perf",
@@ skipping 116 matching lines @@
       "checkout",
       "-f",
       "FETCH_HEAD"
     ],
     "cwd": "[SLAVE_BUILD]/swarming.client",
     "name": "git checkout (swarming_client)"
   },
   {
     "cmd": [
       "git",
+      "rev-parse",
+      "HEAD"
+    ],
+    "cwd": "[SLAVE_BUILD]/swarming.client",
+    "name": "read revision",
+    "stdout": "/path/to/tmp/",
+    "~followup_annotations": [
+      "@@@STEP_TEXT@<br/>checked out 'deadbeef'<br/>@@@"
+    ]
+  },
+  {
+    "cmd": [
+      "git",
       "clean",
       "-f",
       "-d",
       "-x"
     ],
     "cwd": "[SLAVE_BUILD]/swarming.client",
     "name": "git clean (swarming_client)"
   },
   {
     "cmd": [
@@ skipping 952 matching lines @@
       "@@@STEP_LINK@shard #0 isolated out@blah@@@",
       "@@@STEP_FAILURE@@@"
     ]
   },
   {
     "name": "$result",
     "reason": "Step('ct-1k-task-2 on Ubuntu-14.04') failed with return_code 1",
     "status_code": 1
   }
 ]