fix(generator-cli): retain Go /vN module suffix in SDK-Name header and README under --version AUTO

[devin-ai-integration]

Description

Under --version AUTO, a Go SDK is generated with the major-zero placeholder (v0.0.0-fern-placeholder), so the generator emits the module path with no /vN suffix anywhere. generator-cli retrofits the suffix afterward, but addGoMajorVersionSuffix only rewrote go.mod and import lines in .go files. It missed two other places the module path is emitted:

• the X-Fern-SDK-Name header value — a plain (non-import) string literal: headers.Set("X-Fern-SDK-Name", "github.com/org/repo")
• the README (README.md) — go get install command and quoted import samples (README is not a .go file, so the walk skipped it entirely)

Result for a v4 module: the header shipped as github.com/org/repo (missing /v4), the README import example didn't compile when copy-pasted, and the User-Agent (which is "<modulePath>/<version>") looked wrong (.../v4.19.0) because the name half lost its /v4.

This is distinct from #16964 (which strips /vN diff churn before FAI analysis to avoid a false breaking-change) — that fixes classification, not the shipped output format.

Changes Made

• addGoMajorVersionSuffix now also rewrites non-import module-path string literals in .go files and Markdown docs, in addition to imports and go.mod.
• .go files: import lines get the suffix on both the bare path and subpackage paths (unchanged); non-import lines only get the bare "<modulePath>" literal rewritten (covers X-Fern-SDK-Name). The composite User-Agent value "<modulePath>/<version>" is deliberately left alone so it doesn't become .../v4/v4.19.0.
• New Markdown pass (README.md etc.): rewrites go get/go install commands and quoted import samples. Web URLs (e.g. https://pkg.go.dev/<modulePath>) are untouched because the module path there is neither quote-anchored nor preceded by an install command.

Pseudo-diff of the effect on a generated v4 Go SDK:

  // core/request_option.go
- headers.Set("X-Fern-SDK-Name", "github.com/org/repo")
+ headers.Set("X-Fern-SDK-Name", "github.com/org/repo/v4")
  headers.Set("User-Agent", "github.com/org/repo/v4.19.0")   // unchanged

  // README.md
- go get github.com/org/repo
+ go get github.com/org/repo/v4
- import lattice "github.com/org/repo"
+ import lattice "github.com/org/repo/v4"

• Updated README.md generator (if applicable) — README rewriting handled in addSuffixToMarkdownFile

Testing

• Unit tests added/updated — 3 new tests in the addGoMajorVersionSuffix suite: SDK-Name header literal gets /v4; composite User-Agent is not double-suffixed; README go get + import samples get /v4 while the pkg.go.dev badge URL is left intact.
• Manual testing completed — full @fern-api/generator-cli suite green (452 passed, 1 skipped).

Link to Devin session: https://app.devin.ai/sessions/d7363ebb78134b23b785a4750dd9ea06
Requested by: @dvdaruri-art

---

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring

[nitpickybot]

AI Review Summary

The PR extends the Go /vN suffix retrofit to cover non-import string literals in .go files and Markdown docs. Logic is generally sound with quote-anchoring to avoid prefix corruption, but there's a double-suffixing risk on the bare-literal replacement for both .go and Markdown files when the path is already versioned.

• 🟡 1 warning(s)
• 🔵 1 suggestion(s)

[nitpickybot]

🟡 warning

The quoted-import replacement here has no guard against an already-suffixed path. If modulePath is github.com/org/repo and the README already contains "github.com/org/repo/v4" (or "github.com/org/repo/v4/client"), the "${modulePath}/ split will turn it into "github.com/org/repo/v4/v4/.... The go get regex uses a negative lookahead to prevent exactly this, but the quoted path handling does not. Idempotency matters if this ever runs twice or on partially-suffixed input.

[nitpickybot]

🔵 suggestion

Same double-suffix concern as the Markdown path: .split("${modulePath}/) on an import line that's already "<modulePath>/v4/client" produces "<modulePath>/v4/v4/client". Fine under the documented AUTO placeholder flow (always unsuffixed), but the operation isn't idempotent. Worth a lookahead-style guard or an early check for an existing /vN segment.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 1 additional finding.