Also, props for the comment before the hack:

  # Horrible hack, I will go to hell for this.  The bots need to have a git
  # cache set up; but how can we tell whether this code is running on a bot
  # or a developer's machine?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/61c4695062d918b68b46e2b49ac9c3be56370b3e

commit 61c4695062d918b68b46e2b49ac9c3be56370b3e
Author: Don Garrett <dgarrett@google.com>
Date: Tue Jun 19 21:38:42 2018

gclient: Stop using implicit git_cache_dir.

Start passing in the git cache directly explicitly, or else not using
git cache. Further, continue to use a made up directory in /tmp if
inside the chroot, since we don't map the git cache directory into the
dchroot (this mostly only applies to unittests, I think).

Also, update all of the call chains to pass along the git cache
directory, which is being explicitly passed to cbuildbot on the
command line.

BUG= chromium:853391 
TEST=run_tests

Change-Id: I96544e1b224bdd5c4a746ad02135db02fbdf461f
Reviewed-on: https://chromium-review.googlesource.com/1103551
Commit-Ready: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>

[modify] https://crrev.com/61c4695062d918b68b46e2b49ac9c3be56370b3e/cros_bisect/simple_chrome_builder.py
[modify] https://crrev.com/61c4695062d918b68b46e2b49ac9c3be56370b3e/cbuildbot/commands.py
[modify] https://crrev.com/61c4695062d918b68b46e2b49ac9c3be56370b3e/cros_bisect/simple_chrome_builder_unittest.py
[modify] https://crrev.com/61c4695062d918b68b46e2b49ac9c3be56370b3e/scripts/sync_chrome.py
[modify] https://crrev.com/61c4695062d918b68b46e2b49ac9c3be56370b3e/lib/gclient.py
[modify] https://crrev.com/61c4695062d918b68b46e2b49ac9c3be56370b3e/lib/gclient_unittest.py
[modify] https://crrev.com/61c4695062d918b68b46e2b49ac9c3be56370b3e/cbuildbot/stages/chrome_stages.py

Hopefully fixed.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/84e07da8461b4b76da32670f411417a117a8340c

commit 84e07da8461b4b76da32670f411417a117a8340c
Author: Chromite Chromium Autoroll <chromite-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Tue Jun 19 23:46:40 2018

Roll src/third_party/chromite efd58885b78d..9cccc5ce4fb9 (7 commits)

https://chromium.googlesource.com/chromiumos/chromite.git/+log/efd58885b78d..9cccc5ce4fb9


git log efd58885b78d..9cccc5ce4fb9 --date=short --no-merges --format='%ad %ae %s'
2018-06-19 ayatane@chromium.org sysmon: Ignore chromeos3-* devservers
2018-06-19 dgarrett@google.com gclient: Stop using implicit git_cache_dir.
2018-06-19 lhchavez@google.com Add 'signed' image type examples / docs to cros flash
2018-06-19 dgarrett@google.com chromeos_config: Move toolchain builders to swarming.
2018-06-19 dgarrett@google.com build_status: Remove config_lib.UseBuildbucketScheduler.
2018-06-19 yunlian@google.com cros_gdb: set debug-file-directory for simple chrome.
2018-06-19 vapier@chromium.org pylintrc: convert warnings list into readable ids


Created with:
  gclient setdep -r src/third_party/chromite@9cccc5ce4fb9

The AutoRoll server is located here: https://chromite-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.



BUG= chromium:853866 , chromium:853391 ,chromium:852017, chromium:853969 , chromium:853025 , chromium:843275 ,chromium:None
TBR=chrome-os-gardeners@chromium.org

Change-Id: I38b6b86c7271b9ca0ec2148faa144816e012ac81
Reviewed-on: https://chromium-review.googlesource.com/1107006
Reviewed-by: Chromite Chromium Autoroll <chromite-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: Chromite Chromium Autoroll <chromite-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#568648}
[modify] https://crrev.com/84e07da8461b4b76da32670f411417a117a8340c/DEPS

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1

commit c4424eb6803d9ffcbaea6b295d680d0fe56c4df1
Author: Don Garrett <dgarrett@chromium.org>
Date: Wed Jun 20 17:46:43 2018

Revert "gclient: Stop using implicit git_cache_dir."

This reverts commit 61c4695062d918b68b46e2b49ac9c3be56370b3e.

Reason for revert: Speculative revert related to GoB quota issues.  https://crbug.com/854652 

Original change's description:
> gclient: Stop using implicit git_cache_dir.
> 
> Start passing in the git cache directly explicitly, or else not using
> git cache. Further, continue to use a made up directory in /tmp if
> inside the chroot, since we don't map the git cache directory into the
> dchroot (this mostly only applies to unittests, I think).
> 
> Also, update all of the call chains to pass along the git cache
> directory, which is being explicitly passed to cbuildbot on the
> command line.
> 
> BUG= chromium:853391 
> TEST=run_tests
> 
> Change-Id: I96544e1b224bdd5c4a746ad02135db02fbdf461f
> Reviewed-on: https://chromium-review.googlesource.com/1103551
> Commit-Ready: Don Garrett <dgarrett@chromium.org>
> Tested-by: Don Garrett <dgarrett@chromium.org>
> Reviewed-by: Don Garrett <dgarrett@chromium.org>

Bug:  chromium:853391 
Change-Id: Ibabaffc49edf891ee7e6b2259fdd3020d85b55c3
Reviewed-on: https://chromium-review.googlesource.com/1108391
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>

[modify] https://crrev.com/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1/cros_bisect/simple_chrome_builder.py
[modify] https://crrev.com/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1/cbuildbot/commands.py
[modify] https://crrev.com/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1/cros_bisect/simple_chrome_builder_unittest.py
[modify] https://crrev.com/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1/scripts/sync_chrome.py
[modify] https://crrev.com/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1/lib/gclient.py
[modify] https://crrev.com/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1/lib/gclient_unittest.py
[modify] https://crrev.com/c4424eb6803d9ffcbaea6b295d680d0fe56c4df1/cbuildbot/stages/chrome_stages.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/269723a243b00fd0266272db98f9e2cac4515aa9

commit 269723a243b00fd0266272db98f9e2cac4515aa9
Author: Chromite Chromium Autoroll <chromite-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Wed Jun 20 20:35:43 2018

Roll src/third_party/chromite 29f54a30992a..c4424eb6803d (2 commits)

https://chromium.googlesource.com/chromiumos/chromite.git/+log/29f54a30992a..c4424eb6803d


git log 29f54a30992a..c4424eb6803d --date=short --no-merges --format='%ad %ae %s'
2018-06-20 dgarrett@chromium.org Revert "gclient: Stop using implicit git_cache_dir."
2018-06-20 derat@chromium.org cbuildbot: Add run_tast.sh to SSP archive.


Created with:
  gclient setdep -r src/third_party/chromite@c4424eb6803d

The AutoRoll server is located here: https://chromite-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.



BUG= chromium:853391 ,chromium:none
TBR=chrome-os-gardeners@chromium.org

Change-Id: Ia0e4155e215863c744afd84a0b2326306a2d0941
Reviewed-on: https://chromium-review.googlesource.com/1108222
Reviewed-by: Chromite Chromium Autoroll <chromite-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: Chromite Chromium Autoroll <chromite-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#568995}
[modify] https://crrev.com/269723a243b00fd0266272db98f9e2cac4515aa9/DEPS