common: stamp build time + commit, log build info in every build

[myleshorton]

What

• Add common.BuildTime + common.Commit vars (ldflags-injected, alongside Version).
• Remove the if Dev() gate on build/dependency logging (added incidentally in Linux daemon and systemd service #301) so it runs in every build.
• On startup, log a concise build banner (version, buildTime, commit, goVersion, mainModule) at Info, plus the linked versions of the load-bearing deps (keepcurrent, amp, domainfront, kindling, lantern-box, sing-box) at Info; the full dependency list stays at Debug (so no per-dep spam in prod).

Why

A 9.1.14 iOS TestFlight build shipped a pre-fix keepcurrent (54a4d9a, the send-on-closed-channel crash) even though go.mod declared the fixed f204338. Because logModuleInfo() was gated behind Dev(), beta/prod builds logged nothing about their actual linked deps — the stale build was invisible until a crash stack happened to reveal the version. debug.ReadBuildInfo() reflects what is really linked into the binary, so surfacing it makes stale-build regressions visible directly.

Pairs with getlantern/lantern's Makefile change that injects the new ldflags.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WGpKfgkbfdJwwsTaouMDoR

Summary by CodeRabbit

• New Features
  • App startup now includes more detailed build metadata in logs, such as version, build time, commit, Go version, and main module info.
  • Important linked dependencies are highlighted more prominently in startup logs, while full dependency details remain available at a lower log level.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 05e392e9-effc-4cd5-8aa4-68c734c1d8f5

📥 Commits

Reviewing files that changed from the base of the PR and between ce70c50 and 47efbcd.

📒 Files selected for processing (2)

• common/constants.go
• common/init.go

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📝 Walkthrough

Walkthrough

Adds BuildTime and Commit package-level variables to common/constants.go for ldflags injection, and replaces the prior Dev-only logModuleInfo() in common/init.go with an always-on logBuildInfo() that logs build identity and filters dependency logging via a new loadBearingDeps allowlist.

Changes

Build Metadata Logging

Layer / File(s)	Summary
Build metadata variables common/constants.go	Adds exported BuildTime and Commit variables defaulting to "unknown", documented for ldflags injection at build time.
Init wiring and build info logging common/init.go	Init now unconditionally calls new logBuildInfo(), which reads build info via debug.ReadBuildInfo(), logs version/build/commit/module details, and logs dependencies at Info level if listed in a new loadBearingDeps allowlist or Debug level otherwise; replaces the previous Dev-only logModuleInfo().

Estimated code review effort: 2 (Simple) | ~10 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Init
  participant logBuildInfo
  participant ReadBuildInfo as debug.ReadBuildInfo
  participant Logger

  Init->>logBuildInfo: call on startup
  logBuildInfo->>ReadBuildInfo: request build info
  ReadBuildInfo-->>logBuildInfo: return info or failure
  alt info available
    logBuildInfo->>Logger: log Version, BuildTime, Commit, GoVersion, Main
    loop each dependency
      logBuildInfo->>Logger: log at Info (load-bearing) or Debug (other)
    end
  else info unavailable
    logBuildInfo->>Logger: log "no build info" message
  end

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main changes: added build metadata stamping and always-on build info logging.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fisk/build-stamp

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[Copilot]

Pull request overview

This PR makes Radiance binaries self-describing by adding ldflags-injected build identity fields and emitting build + dependency linkage information on startup in all builds (not just Dev), so mismatched/stale linked dependencies are visible directly in logs.

Changes:

• Add common.BuildTime and common.Commit build-time variables (ldflags-injected alongside Version).
• Replace the Dev-only debug.ReadBuildInfo() logging with logBuildInfo() that runs in every build.
• Log a concise build banner at Info and log dependency versions (Info for selected “load-bearing” deps; Debug for full list).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
common/init.go	Always logs build identity + linked module versions at startup (Info for selected deps, Debug for full list).
common/constants.go	Adds ldflags-injected BuildTime and Commit variables to capture build identity.

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