xtask: Add github module

Author: nicholasbishop

xtask/src/github.rs

@@ -0,0 +1,67 @@
+use anyhow::{bail, Context, Result};
+use serde::Deserialize;
+use ureq::Agent;
+
+/// Name of the github organization for this repo.
+const ORG: &str = "rust-osdev";
+
+/// Name of this repo on github.
+const REPO: &str = "ovmf-prebuilt";
+
+/// User-Agent header to send with requests.
+const USER_AGENT: &str = "https://github.com/rust-osdev/ovmf-prebuilt";
+
+#[derive(Debug, Deserialize)]
+struct Asset {
+    digest: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct Release {
+    pub tag_name: String,
+    name: Option<String>,
+    assets: Vec<Asset>,
+}
+
+impl Release {
+    pub fn sha256(&self) -> Result<&str> {
+        if self.assets.len() != 1 {
+            bail!("expected exactly one asset, got {}", self.assets.len());
+        }
+        let asset = &self.assets[0];
+        let digest = asset.digest.as_ref().context("asset is missing digest")?;
+        digest
+            .strip_prefix("sha256:")
+            .context("digest format is not sha256")
+    }
+}
+
+pub struct Github {
+    agent: Agent,
+}
+
+impl Github {
+    pub fn new() -> Self {
+        let config = Agent::config_builder().user_agent(USER_AGENT).build();
+        let agent = Agent::new_with_config(config);
+        Github { agent }
+    }
+
+    pub fn get_releases(&self) -> Result<Vec<Release>> {
+        let url = format!("https://api.github.com/repos/{ORG}/{REPO}/releases");
+        println!("downloading release list");
+        let mut releases: Vec<Release> = self
+            .agent
+            .get(url)
+            .header("Accept", "application/vnd.github+json")
+            .header("X-GitHub-Api-Version", "2022-11-28")
+            .call()?
+            .body_mut()
+            .read_json()?;
+        // Remove releases with a null `name`. This serves to exclude older
+        // releases (with tags like "v0.20211216.194+gcc2db6ebfb"), from
+        // before the repo was reworked to its current form.
+        releases.retain(|release| release.name.is_some());
+        Ok(releases)
+    }
+}

xtask/src/main.rs

@@ -1,3 +1,6 @@
+#[expect(dead_code)]
+mod github;
+
 use anyhow::{anyhow, bail, Result};
 use clap::{Args, Parser, Subcommand};
 use std::fs;