If a ref is incorrectly set, it will affect later runs. For example, [1] caused a bad refspec to be added to the fetch config, (+refs/branch-heads/refs/branch-heads/6.7:refs/branch-heads/refs/branch-heads/6.7) which affects all subsequent runs in the same bot: [2], [3]. This makes bot_update clear the fetch config before each run, so it is more robust against these kind of failures. [1] https://logs.chromium.org/v/?s=v8%2Fbuildbucket%2Fcr-buildbucket.appspot.com%2F8942033142534034848%2F%2B%2Fsteps%2Fbot_update%2F0%2Fstdout [2] https://logs.chromium.org/v/?s=v8%2Fbuildbucket%2Fcr-buildbucket.appspot.com%2F8941307871443322944%2F%2B%2Fsteps%2Fbot_update%2F0%2Fstdout [3] https://logs.chromium.org/v/?s=v8%2Fbuildbucket%2Fcr-buildbucket.appspot.com%2F8941333453153279680%2F%2B%2Fsteps%2Fbot_update%2F0%2Fstdout Bug: 862547 Change-Id: I2f849c604656e81ebd7377465d287226b8bdea1a Reviewed-on: https://chromium-review.googlesource.com/1135645 Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org> Reviewed-by: Aaron Gable <agable@chromium.org> Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
