Add .env file support

[jbsmith7741]

Quality check

• Documentation included
• Test coverage

Summary

Adds support for loading a working-directory .env file when OptEnv is enabled, alongside existing environment-variable mapping.

• Introduces a dotenv parser (internal/encode/env/dotenv.go) with quoted-value handling and inline-comment trimming; a follow-up commit tightens quote edge cases.
• Load / LoadEnv now apply .env values per struct field (non-empty .env entries override os.Getenv for that key) before file and flag sources.
• Extends env encode/decode and file decode wiring; updates config.go load-order comments.
• Adds dotenv_test.go and related env tests; refreshes fixture configs under test/.

---

Note

Medium Risk
Changes how environment-style config is decoded (flat GetVal vs prior nested env mapping) and introduces new parsing rules that affect load order and field population when .env or OptEnv is used.

Overview
Adds a dotenv parser and wires .env files into config loading: file.Load and -c paths with a .env extension use LoadEnvFile, which parses keys/values (quotes, escapes, inline comments) and maps them through the env Decoder via an injectable GetVal hook.

The env decoder now resolves values through GetVal (default os.Getenv) instead of the old recursive populate helper; env encode quotes strings when needed. Public docs describe cwd .env under OptEnv/LoadEnv, and tests/fixtures cover dotenv parsing plus loading test/.env. CI bumps Go versions (module go 1.18, trial v0.8.0).

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 26.35%. Comparing base (3bcfc37) to head (fe5c348).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   23.87%   26.35%   +2.48%     
==========================================
  Files           1        1              
  Lines         155      148       -7     
==========================================
+ Hits           37       39       +2     
+ Misses        105       96       -9     
  Partials       13       13              

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[jbsmith7741]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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[cursor]

Nested struct env mapping removed

High Severity

Decoder.Unmarshal no longer recurses into nested structs or applies env prefixes / omitprefix, after populate was removed. Nested fields (e.g. LEVEL2_*, embedded structs, documented omitprefix layouts) are not filled from the environment unless the parent struct implements encoding.TextUnmarshaler.

 

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