Embed the git commit in fj-app's version number

.github/workflows/cd.yml

@@ -2,7 +2,7 @@ name: Continuous Deployment
 
 on:
   push:
-    branches: [ main ]
+    branches: [main]
 
 env:
   CARGO_TERM_COLOR: always
@@ -11,6 +11,10 @@ env:
   # used to rename and upload the binaries
   PROJ_NAME: fj-app
 
+  # This lets our app know it's an "official" release. Otherwise we would get
+  # a version number like "fj-app 0.8.0 (8cb928bb, unreleased)"
+  FJ_OFFICIAL_RELEASE: 1
+
 defaults:
   run:
     shell: bash

crates/fj-app/build.rs

@@ -0,0 +1,81 @@
+use std::{
+    path::PathBuf,
+    process::{Command, Output, Stdio},
+};
+
+fn main() {
+    println!("cargo:rustc-env=FJ_VERSION_STRING={}", version_string());
+}
+
+fn version_string() -> String {
+    let pkg_version = std::env::var("CARGO_PKG_VERSION").unwrap();
+    let commit = git_description();
+
+    let official_release =
+        std::env::var("FJ_OFFICIAL_RELEASE").as_deref() == Ok("1");
+    println!("cargo:rerun-if-env-changed=FJ_OFFICIAL_RELEASE");
+
+    match (commit, official_release) {
+        (Some(commit), true) => format!("{pkg_version} ({commit})"),
+        (Some(commit), false) => {
+            format!("{pkg_version} ({commit}, unreleased)")
+        }
+        (None, true) => pkg_version,
+        (None, false) => format!("{pkg_version} (unreleased)"),
+    }
+}
+
+/// Try to get the current git commit.
+///
+/// This may fail if `git` isn't installed (unlikely) or if the `.git/` folder
+/// isn't accessible (more likely than you think). This typically happens when
+/// we're building just the `fj-app` crate in a Docker container or when
+/// someone is installing from crates.io via `cargo install`.
+fn git_description() -> Option<String> {
+    let crate_dir = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap());
+
+    let mut cmd = Command::new("git");
+    cmd.args(["describe", "--always", "--dirty=-modified"])
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .current_dir(&crate_dir);
+
+    let Output {
+        status,
+        stdout,
+        stderr,
+    } = cmd.output().ok()?;
+
+    let stdout = String::from_utf8_lossy(&stdout);
+
+    if !status.success() {
+        // Not sure if anyone will ever see this, but it could be helpful for
+        // troubleshooting.
+        eprintln!("Command failed: {cmd:?}");
+        let stderr = String::from_utf8_lossy(&stderr);
+        eprintln!("---- Stdout ----");
+        eprintln!("{stdout}");
+        eprintln!("---- Stderr ----");
+        eprintln!("{stderr}");
+        return None;
+    }
+
+    // Make sure we re-run whenever the current commit changes
+    let project_root = crate_dir.ancestors().nth(2).unwrap();
+    let head_file = project_root.join(".git").join("HEAD");
+    println!("cargo:rerun-if-changed={}", head_file.display());
+
+    if let Ok(contents) = std::fs::read_to_string(&head_file) {
+        // Most of the time the HEAD file will be `ref: refs/heads/$branch`, but
+        // when it's a detached head we'll only get the commit hash and can skip
+        // the rerun-if-changed logic.
+
+        if let Some((_, branch)) = contents.split_once(' ') {
+            let commit_hash_file =
+                project_root.join(".git").join(branch.trim());
+            println!("cargo:rerun-if-changed={}", commit_hash_file.display());
+        }
+    }
+
+    Some(stdout.trim().to_string())
+}

crates/fj-app/src/args.rs

@@ -7,6 +7,7 @@ use fj_math::Scalar;
 
 /// Fornjot - Experimental CAD System
 #[derive(clap::Parser)]
+#[clap(version = env!("FJ_VERSION_STRING"))]
 pub struct Args {
     /// The model to open
     #[clap(short, long)]