//! Derive the git version at build time via `semvertag-shell`.
//!
//! Calls `git describe --tags --long --always --dirty=.dirty` through the
//! `semvertag-shell` adapter, which rewrites the output into a correctly-ordered
//! SemVer string (e.g. `0.2.1-dev.3+g87af40b` past a release, `0.2.1` at a
//! tagged commit, or `0.2.0+dirty` for a dirty worktree at the tag).
//!
//! The result is exposed as `PLANR_VERSION` so the CLI can print it via
//! `planr --version`. Falls back to the Cargo.toml `package.version` when git
//! is unreachable (no `.git` directory, shallow clone, missing binary, etc.)
//! so the build never fails.