Add Vite build plugin to generate version.txt

vite.config.ts

@@ -1,7 +1,9 @@
-import { defineConfig } from 'vite';
+import { defineConfig, Plugin } from 'vite';
 import solidPlugin from 'vite-plugin-solid';
 import { dirname, resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
+import { exec } from 'node:child_process';
+import { promisify } from 'node:util';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 
@@ -22,5 +24,68 @@ export default defineConfig({
       '/api': 'http://localhost:3001',
     },
   },
-  plugins: [solidPlugin()],
+  plugins: [solidPlugin(), versionPlugin()],
 });
+
+function versionPlugin(): Plugin {
+  return {
+    name: 'generate-version',
+    apply: 'build',
+    async generateBundle() {
+      this.emitFile({
+        type: 'asset',
+        fileName: 'version.txt',
+        source: await getVersionInfo(),
+      });
+    },
+  };
+}
+
+async function getVersionInfo(): Promise<string> {
+  const info: Record<string, string> = {
+    build: new Date().toISOString(),
+  };
+
+  const execAsync = promisify(exec);
+
+  const fromJujutsu = async () => {
+    const template = [
+      'change_id.short()',
+      'commit_id.short()',
+      'committer.timestamp().format("%Y-%m-%d")',
+      'description.first_line()',
+    ].join(' ++ "\\t" ++ ');
+    const { stdout } = await execAsync(
+      `jj log -r '::@ & ~description("")' -n1 --no-graph -T '${template}'`
+    );
+    const [change, hash, date, msg] = stdout.trim().split('\t');
+    info.change = change;
+    info.hash = hash;
+    info.commit = `${msg} (${date})`;
+  };
+
+  const fromGit = async () => {
+    const { stdout } = await execAsync(
+      'git log --format="%h%x09%cs%x09%s" -n 1'
+    );
+    const [hash, date, msg] = stdout.trim().split('\t');
+    info.hash = hash;
+    info.commit = `${msg} (${date})`;
+  };
+
+  try {
+    await fromJujutsu();
+  } catch {
+    try {
+      await fromGit();
+    } catch {
+      // No VCS available
+    }
+  }
+
+  return (
+    Object.entries(info)
+      .map(([k, v]) => `${k}: ${v}`)
+      .join('\n') + '\n'
+  );
+}