use libgit2 to track PRs (#10)v0.2.0

* nix: don't depend on registry for nixpkgs input

* use libgit2 to track PRs

* nix: don't use ci devShell as defaul

* crates: bump serenity from `9ad74d4` to `0.12.2

* nix: fix cross compiled builds

* crates: split more from client

* bot-jobs: update remote refs more efficiently

* git-tracker: account for HEAD commits

* bot-config: use nixpkgs branches from environment

* bot-commands: don't display branches prs haven't landed in

* git-tracker: return false when commits aren't found

this is annoying as a hard error since it turns out github will report
garbage merge commit SHAs for PRs that *haven't* been merged yet. yay

* bot: improve docs in some places

* bot-client: display invite link on start

* bot-http: add TeawieClientExt

* bot-commands: add /about

* docs: update readme todos

* nix: enable StateDirectory in module

* crates: bump to 0.2.0

1 files changed, 121 insertions, 0 deletions

diff --git a/crates/bot-commands/src/track.rs b/crates/bot-commands/src/track.rs
new file mode 100644
index 0000000..1f22d0e
--- /dev/null
+++ b/crates/bot-commands/src/track.rs
@@ -0,0 +1,121 @@
+use bot_config::Config;
+use bot_consts::{NIXPKGS_REMOTE, NIXPKGS_URL};
+use bot_error::Error;
+use bot_http::{self as http, GithubClientExt};
+use git_tracker::Tracker;
+
+use log::trace;
+use serenity::all::CreateEmbed;
+use serenity::builder::{CreateCommand, CreateCommandOption, CreateInteractionResponseFollowup};
+use serenity::model::application::{
+	CommandInteraction, CommandOptionType, InstallationContext, ResolvedOption, ResolvedValue,
+};
+use serenity::prelude::Context;
+
+const REPO_OWNER: &str = "NixOS";
+const REPO_NAME: &str = "nixpkgs";
+
+/// Collect the status of the commit SHA [`commit_sha`] in each of the nixpkgs
+/// branches in [`branches`], using the repository at path [`repository_path`]
+///
+/// # Errors
+///
+/// Will return [`Err`] if we can't start tracking a repository at the given path,
+/// or if we can't determine if the branch has given commit
+fn collect_statuses_in<'a>(
+	repository_path: &str,
+	commit_sha: &str,
+	branches: impl IntoIterator<Item = &'a String>,
+) -> Result<Vec<String>, Error> {
+	// start tracking nixpkgs
+	let tracker = Tracker::from_path(repository_path)?;
+
+	// check to see what branches it's in
+	let mut status_results = vec![];
+	for branch_name in branches {
+		trace!("Checking for commit in {branch_name}");
+		let full_branch_name = format!("{NIXPKGS_REMOTE}/{branch_name}");
+		let has_pr = tracker.branch_contains_sha(&full_branch_name, commit_sha)?;
+
+		if has_pr {
+			status_results.push(format!("`{branch_name}` ✅"));
+		}
+	}
+
+	Ok(status_results)
+}
+
+pub async fn respond(
+	ctx: &Context,
+	http: &http::Client,
+	config: &Config,
+	command: &CommandInteraction,
+) -> Result<(), Error> {
+	// this will probably take a while
+	command.defer(&ctx).await?;
+
+	let options = command.data.options();
+	let Some(ResolvedOption {
+		value: ResolvedValue::Integer(pr),
+		..
+	}) = options.first()
+	else {
+		let resp = CreateInteractionResponseFollowup::new()
+			.content("Please provide a valid pull request!");
+		command.create_followup(&ctx, resp).await?;
+
+		return Ok(());
+	};
+
+	let Ok(pr_id) = u64::try_from(*pr) else {
+		let resp =
+			CreateInteractionResponseFollowup::new().content("PR numbers aren't negative...");
+		command.create_followup(&ctx, resp).await?;
+
+		return Ok(());
+	};
+
+	// find out what commit our PR was merged in
+	let Some(commit_sha) = http.merge_commit_for(REPO_OWNER, REPO_NAME, pr_id).await? else {
+		let response = CreateInteractionResponseFollowup::new()
+			.content("It seems this pull request is very old. I can't track it");
+		command.create_followup(&ctx, response).await?;
+
+		return Ok(());
+	};
+
+	let status_results = collect_statuses_in(
+		&config.nixpkgs_path,
+		&commit_sha,
+		config.nixpkgs_branches.iter(),
+	)?;
+
+	// if we don't find the commit in any branches from above, we can pretty safely assume
+	// it's an unmerged PR
+	let embed_description: String = if status_results.is_empty() {
+		"It doesn't look like this PR has been merged yet! (or maybe I just haven't updated)"
+			.to_string()
+	} else {
+		status_results.join("\n")
+	};
+
+	let embed = CreateEmbed::new()
+		.title(format!("Nixpkgs PR #{} Status", *pr))
+		.url(format!("{NIXPKGS_URL}/pull/{pr}"))
+		.description(embed_description);
+
+	let resp = CreateInteractionResponseFollowup::new().embed(embed);
+	command.create_followup(&ctx, resp).await?;
+
+	Ok(())
+}
+
+pub fn register() -> CreateCommand {
+	CreateCommand::new("track")
+		.description("Track a nixpkgs PR")
+		.add_integration_type(InstallationContext::User)
+		.add_option(
+			CreateCommandOption::new(CommandOptionType::Integer, "pull_request", "PR to track")
+				.required(true),
+		)
+}