Might be appropriate to stick this file in XDG_CONFIG_HOME (~/.config) and/or XDG_CONFIG_DIRS (/etc/xdg)?

Otherwise SGTM!

We don't actually set those env vars, so I'll change the garcon startup script to set XDG_CONFIG_HOME to be ~/.config and then use that in garcon. I'll then create a cros-garcon.conf file in that dir with contents like this:

[core]
DisableAutomaticCrosPackageUpdates=false

And then it looks like adding that to the conffiles in the debian package will prevent changes from being overwritten by us on package upgrades. :)

And then I'd reload this and check the setting every time I was about to do an auto update.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/f33f5d4b9433d123158d1e06b3ef252db74a141b

commit f33f5d4b9433d123158d1e06b3ef252db74a141b
Author: Jeffrey Kardatzke <jkardatzke@google.com>
Date: Tue Aug 07 08:51:26 2018

vm_tools: garcon: Add config setting for disabling auto updates

This checks the ~/.config/cros-garcon.conf file for a line of
DisableAutomaticCrosPackageUpdates=true and if that is present then it
disables doing the automatic updating of the cros packages.

BUG= chromium:865106 
TEST=Verified manually on eve

Change-Id: Ic83fe4ef530e151b265371a0a038e38578179e11
Reviewed-on: https://chromium-review.googlesource.com/1152488
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: Stephen Barber <smbarber@chromium.org>

[modify] https://crrev.com/f33f5d4b9433d123158d1e06b3ef252db74a141b/vm_tools/garcon/package_kit_proxy.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/containers/cros-container-guest-tools/+/05eaf0df60026b8bbddebe901348be4d49cea6d1

commit 05eaf0df60026b8bbddebe901348be4d49cea6d1
Author: Jeffrey Kardatzke <jkardatzke@google.com>
Date: Fri Aug 31 12:23:20 2018

cros-garcon: Add install of cros-garcon.conf config file

This installs a config file for garcon to the ~/.config folder for the
main user if it does not exist. We don't remove it on uninstall in order
to preserve any changes the user has made.

BUG= chromium:865106 
TEST=Built .deb and verified installs correctly
CQ-DEPEND=CL:1191865

Change-Id: I68c2833151176701c885148de8be3628d77dd848
Reviewed-on: https://chromium-review.googlesource.com/1191866
Commit-Ready: Jeffrey Kardatzke <jkardatzke@google.com>
Tested-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: Stephen Barber <smbarber@chromium.org>

[modify] https://crrev.com/05eaf0df60026b8bbddebe901348be4d49cea6d1/cros-garcon/postinst
[modify] https://crrev.com/05eaf0df60026b8bbddebe901348be4d49cea6d1/cros-garcon/conffiles
[modify] https://crrev.com/05eaf0df60026b8bbddebe901348be4d49cea6d1/cros-garcon/BUILD
[add] https://crrev.com/05eaf0df60026b8bbddebe901348be4d49cea6d1/cros-garcon/skel.cros-garcon.conf
[modify] https://crrev.com/05eaf0df60026b8bbddebe901348be4d49cea6d1/cros-garcon/cros-garcon-override.conf