Automate more of Sonatype setup

[nightscape]

Following up on your How To Publish to Maven Central Easily with Mill blog post, I'd like to propose a few additional automations:

• initGpgKeys now auto-detects developer name, email, and URL from pomSettings and pre-fills the prompts, so users can just press Enter to accept defaults
• After key generation, the command offers to write credentials directly into detected shell config files (bash, zsh, fish, nushell, powershell) with a diff preview before applying
• If gh CLI is authenticated, offers to upload secrets directly to the GitHub repository
• Prompts for Sonatype credentials during the same flow instead of requiring users to set them separately
• Users can type "q" at any prompt to abort cleanly
• Keyserver URL is now configurable via --keyserverUrl parameter, allowing tests to use a mock server instead of hitting the real keyserver

Technical details

• New ShellConfiguration utility in libs/util/java11 handles cross-platform shell config detection and atomic env var upsert with proper escaping per shell
• Integration test uses an in-process HTTP mock keyserver instead of relying on keyserver.ubuntu.com
• Keyserver verification uses a bounded retry count (3 attempts) instead of a 60-second deadline loop

Usage of AI

1. Claude Opus 4.6 created the initial plan.
2. I did multiple rounds of manual plan reviews and refinements.
3. Claude generated the implementation.
4. I did multiple rounds of manual and automated code reviews until I was happy with the result.

[Copilot]

Pull request overview

This PR extends Mill’s Sonatype Central publishing setup by enhancing the interactive initGpgKeys flow and adding cross-shell helpers to preview/apply environment-variable configuration automatically.

Changes:

• Add ShellConfiguration utilities to detect shell config files, format env-var lines, and upsert them (with optional diff preview).
• Enhance initGpgKeys to pass POM-derived hints (name/email/url), support configurable keyserver URL, and offer guided local shell + GitHub Actions setup.
• Add unit/integration tests for shell env-var formatting/upsert behavior and the updated initGpgKeys flow (with a mock keyserver).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
libs/util/java11/src/mill/util/ShellConfiguration.scala	New shell detection + env-var formatting/matching + upsert/preview helpers
libs/util/test/src/mill/util/ShellConfigurationTests.scala	Unit tests for escaping, regex matching, and upsert behavior
libs/javalib/src/mill/javalib/SonatypeCentralPublishModule.scala	Extend initGpgKeys command to pass keyserver URL + POM-derived hints
libs/javalib/pgp-worker/src/mill/javalib/pgp/worker/MillInitGpgKeysMain.scala	Expanded interactive workflow (upload/verify, local shell setup, optional gh secret upload)
integration/feature/init-gpg-publish/src/InitGpgPublishTests.scala	Integration test updated to use a local mock keyserver + new output expectations
libs/javalib/package.mill	MiMa exclusion for signature change + add util dependency for pgp-worker

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[nightscape]

@lihaoyi @lefou this is good to review from my side.