feat: inject git describe into dev builds for --version (#208)

[dyoung522]

Summary

• make build now stamps git describe --tags --dirty into the binary via -ldflags -X main.buildDescribe=..., and the Building lmm ... echo line shows the describe string too, so dev builds are visually distinguishable at build time.
• cmd/lmm/root.go: new buildDescribe var (empty by default, static version var UNCHANGED). --version (and any other Cobra surface reading rootCmd.Version) shows the plain static version when buildDescribe is empty or exactly v<version> (a clean tag build); otherwise it appends (dev: <describe>), with -dirty passing through verbatim. JSON surfaces are unaffected (none of them emit the app's own version). The TUI has no version display surface to update.
• Table-driven tests (cmd/lmm/version_test.go) cover empty/clean-tag/ahead/dirty/ahead+dirty. make man produces a zero diff against docs/man/man1 (existing genman drift test also still passes), proving the man pages are untouched by construction.
• README dev section gains a short note that make build self-identifying dev binaries.
• CHANGELOG [Unreleased] entry added.

Closes #208.

Test plan

• go test ./cmd/lmm/... -run TestDisplayVersion -v (new table-driven test, all cases pass)
• make check (fmt, lint, vet, full test suite) — all green
• make man — zero diff vs committed docs/man/man1
• make build && ./lmm --version → lmm version 1.28.0 (dev: v1.28.0-2-g140e3c6-dirty)
• go build -o lmm ./cmd/lmm && ./lmm --version (no ldflags) → lmm version 1.28.0 (unchanged)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR makes developer builds of lmm self-identifying by embedding git describe --tags --dirty at build time and surfacing it via Cobra’s --version, while keeping the static released version (and thus generated man pages) unchanged by default.

Changes:

• Stamp a build-time buildDescribe string via make build/make using -ldflags -X, and show it in the build echo line.
• Add computeDisplayVersion() to conditionally append (dev: <describe>) to the user-facing --version output, plus table-driven tests covering key cases.
• Update README + CHANGELOG to document the new dev build provenance behavior.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
README.md	Documents that make build stamps git provenance so dev binaries self-identify via --version.
Makefile	Adds git describe capture and injects it into the binary via -ldflags -X; updates build output message.
cmd/lmm/version_test.go	Adds table-driven tests for the version/provenance display logic.
cmd/lmm/root.go	Introduces buildDescribe and computeDisplayVersion(), wiring the computed display string into Cobra’s Version.
CHANGELOG.md	Adds an [Unreleased] entry describing the new dev-build provenance stamping behavior.

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[dyoung522]

Fixed in 726d99f — empty parens suppressed via $(if ...).

[dyoung522]

Fixed in 726d99f — --always added; a bare-hash describe renders as 'dev: ' (pinned with a new table case).

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

Suppressed comments (3)

cmd/lmm/root.go:47

• This comment says the Makefile injects git describe --tags --dirty, but the Makefile uses git describe --tags --always --dirty. Updating this keeps the inline documentation accurate (and aligns with the tag-less clone behavior covered by tests).

	// buildDescribe is injected at build time via -ldflags -X (see the
	// Makefile's `build` target) with `git describe --tags --dirty`.
	// Empty for builds made without that ldflags (plain `go build`/`go
	// test`), which display identically to a clean release build.

CHANGELOG.md:13

• CHANGELOG entry documents stamping git describe --tags --dirty, but the Makefile uses git describe --tags --always --dirty (fallback to commit hash when tags are missing). Update the command here to match the implementation.

- `make build` (and `make`) now stamp `git describe --tags --dirty` into the binary via `-ldflags -X`, so `lmm --version` on a dev build self-identifies (e.g. `1.28.0 (dev: v1.28.0-2-g140e3c6-dirty)`) instead of showing the same plain `1.28.0` as a release build — the confusion this fixed came up during the v1.28.0 cycle. A build exactly on the release tag (clean) still shows the plain version; a plain `go build`/`go test` (no ldflags) is unaffected. The static `version` var and man pages are untouched by construction (#208)

README.md:1129

• README claims make build stamps git describe --tags --dirty, but the Makefile actually runs git describe --tags --always --dirty (important for tag-less clones/shallow checkouts). Update the command string here to match the real build behavior.

`make build` (or `make`) is the preferred way to build a working binary: it
stamps `git describe --tags --dirty` into the binary, so `lmm --version` on
a dev build self-identifies as e.g. `1.28.0 (dev: v1.28.0-2-g140e3c6-dirty)`
instead of silently claiming the last released version. A plain
`go build`/`go test` (no ldflags) behaves exactly like a clean release build.