Download multiple versions of OpenTofu in container by default, including 1.6.2, 1.7.1, and 1.8.2

[obscurerichard]

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• I'd be willing to implement this feature (contributing guide)

Describe the user story

As an Atlantis user, I would like multiple versions of OpenTofu to be available in the container, so that I might follow the OpenTofu migration guides as conservatively as possible.

I'm so glad Preinstall opentofu in containers #4337 brought in tofu. However, inspecting the container for v0.31.0 (commit: 245044c) (build date: 2024-11-22T17:58:20.688Z) shows multiple versions of Terraform preinstalled, but not for OpenTofu.

See this terminal transcript for evidence:

/ # tofu --version
OpenTofu v1.8.5
on linux_amd64
/ # tofu
tofu       tofu1.8.5
/ # which tofu
/usr/local/bin/tofu
/ # ls -l /usr/local/bin/tofu*
-rwxr-xr-x    1 root     root      82448384 Nov  4 20:16 /usr/local/bin/tofu
-rwxr-xr-x    1 root     root      82448384 Nov  4 20:16 /usr/local/bin/tofu1.8.5
/ # ls /usr/local/bin
atlantis              terraform             terraform1.8.5        tofu1.8.5
conftest              terraform1.6.6        terraform1.9.8
docker-entrypoint.sh  terraform1.7.5        tofu
/ #

(See also Dockerfile#L121-L130 - fixing this would be really, really easy)

atlantis/Dockerfile

Lines 121 to 130 in b5b95a7

	RUN ./download-release.sh \
	"terraform" \
	"${TARGETPLATFORM}" \
	"${DEFAULT_TERRAFORM_VERSION}" \
	"1.6.6 1.7.5 1.8.5 ${DEFAULT_TERRAFORM_VERSION}" \
	&& ./download-release.sh \
	"tofu" \
	"${TARGETPLATFORM}" \
	"${DEFAULT_OPENTOFU_VERSION}" \
	"${DEFAULT_OPENTOFU_VERSION}"

Describe the solution you'd like
I'd like it if Atlantis pre-installed these versions per the migration instructions for migrating from various versions of Terraform to OpenTofu:

1. 1.6.2 for Migrating from Terraform 1.5.x or lower and Migrating from Terraform 1.6.x
2. 1.7.1 for Migrating from Terraform 1.7.x
3. 1.8.2 for Migrating from Terraform 1.8.x

Describe the drawbacks of your solution
This would make the Dockerfile slightly more complicated, and would bloat the container image size by a couple hundred megabytes.

Describe alternatives you've considered

• Maybe installing the latest minor version of OpenTofu would be sufficient, but I haven't tested the migration instructions with different versions yet.
• If feat: Support project-level Terraform distribution selection feat: Support project-level Terraform distribution selection #5167 gets merged, and if it solves Support OpenTofu auto download Support OpenTofu auto download #4339 this could be a non-issue.