feat: accept snake_case environment variable names

[Abhinesh Jha (Abhineshhh)]

Summary

Implements support for snake_case environment variable names while fully preserving the existing concatenated names for backward compatibility.

Closes / fixes: #248

Problem

Environment variables used a hard-to-read concatenated form (e.g. MPF_SUBSCRIPTIONID). Users requested conventional snake_case (e.g. MPF_SUBSCRIPTION_ID) without breaking existing scripts and CI.

Solution

• Derive both env names from each Cobra flag:
  • Legacy: MPF_ + upper(flagName) → MPF_SUBSCRIPTIONID (unchanged behavior)
  • Snake_case: MPF_ + upper(camelToSnake(flagName)) → MPF_SUBSCRIPTION_ID
• Bind both via Viper BindEnv for every flag (global, ARM, Bicep, Terraform)
• Precedence: CLI flags > legacy env > snake_case env
• Document preferred + legacy forms in the flag reference
• E2E tests accept either form via a small mpfEnv() helper (legacy first)

Examples

Flag	Preferred env	Legacy env (still works)
subscriptionID	MPF_SUBSCRIPTION_ID	MPF_SUBSCRIPTIONID
spClientID	MPF_SP_CLIENT_ID	MPF_SPCLIENTID
templateFilePath	MPF_TEMPLATE_FILE_PATH	MPF_TEMPLATEFILEPATH
tfPath	MPF_TF_PATH	MPF_TFPATH

Changes

Area	Files
CLI binding	cmd/envbinding.go, cmd/rootCmd.go
Unit tests	cmd/envbinding_test.go
Docs	docs/commandline-flags-and-env-variables.md, README.md, AGENTS.md
E2E alignment	e2eTests/env_helpers.go + e2e test files

Backward compatibility

• Existing MPF_SUBSCRIPTIONID, MPF_TFPATH, etc. continue to work
• If both forms are set, legacy wins so current deployments are not surprised
• No flag renames, no dependency changes, no changes to deploy/permission logic under pkg/

Test plan

• go test ./cmd/ -count=1
• go test ./pkg/... -count=1
• go test ./e2eTests/ -count=1 (compile / unit path; live Azure e2e not run in this environment)
• go vet ./cmd/ ./e2eTests/
• gofmt clean on touched Go files
• Unit coverage for: snake_case only, legacy only, both set (legacy wins), CLI overrides env, terraform flags, initializeConfig with root+arm flags

References

• Issue: Feature Request: Support snake_case environment variable names in addition to current format #248
• Related docs updated: docs/commandline-flags-and-env-variables.md

[Copilot]

Pull request overview

Adds support for snake_case environment variables across the azmpf CLI (via Cobra/Viper), while preserving and prioritizing the existing legacy concatenated env var names for backward compatibility (per issue #248).

Changes:

• Implement dual env var binding per flag (legacy + snake_case) with legacy precedence via centralized binding logic in cmd/envbinding.go.
• Add unit coverage for camel→snake conversion, env name derivation, and binding precedence/behavior.
• Align docs and E2E tests to accept either env var form (legacy-first lookup helper).

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
README.md	Updates examples to prefer snake_case env vars while noting legacy compatibility.
docs/commandline-flags-and-env-variables.md	Documents snake_case vs legacy naming rules and lists both env var forms per flag.
cmd/rootCmd.go	Switches config initialization to use the new dual-env binding helper.
cmd/envbinding.go	Introduces camel→snake conversion, env name derivation, and dual BindEnv behavior.
cmd/envbinding_test.go	Adds unit tests for conversion, env name generation, and precedence (CLI > legacy env > snake_case).
e2eTests/env_helpers.go	Adds mpfEnv() helper to read legacy-first, then snake_case env vars in tests.
e2eTests/e2eTerraformWithImportAndTargeting_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraformInvalid_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraformAuthPermissionMismatch_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraformAuthorizationRequestDenied_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eTerraform_test.go	Updates terraform path env lookup to accept both env var forms.
e2eTests/e2eBicepInvalid_test.go	Updates bicep exec path env lookup to accept both env var forms.
e2eTests/e2eBicep_test.go	Updates bicep exec path env lookup to accept both env var forms.
e2eTests/e2eArm_test.go	Updates ARM E2E env var reads to accept both legacy and snake_case forms.
AGENTS.md	Updates agent instructions/examples to use snake_case env vars (preferred).

[Mani Bindra (maniSbindra)]

Abhinesh Jha (@Abhineshhh) Thanks for the PR. It looks good. Can you look that linting PR check which is failing

[Mani Bindra (maniSbindra)]

Abhinesh Jha (@Abhineshhh) Thanks for the PR. It looks good. Can you look that linting PR check which is failing