1 files changed, 95 insertions, 0 deletions
diff --git a/crates/git-tracker/src/managed_repository.rs b/crates/git-tracker/src/managed_repository.rs
new file mode 100644
index 0000000..0a41bd0
--- /dev/null
+++ b/crates/git-tracker/src/managed_repository.rs
@@ -0,0 +1,95 @@
+use git2::{AutotagOption, FetchOptions, RemoteCallbacks, RemoteUpdateFlags, Repository};
+use log::{debug, info, trace, warn};
+use std::{io::Write, path::PathBuf};
+
+// much of this is shamelessly lifted from
+// https://github.com/rust-lang/git2-rs/blob/9a5c9706ff578c936be644dd1e8fe155bdc4d129/examples/pull.rs
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+	#[error("libgit2 error")]
+	Git(#[from] git2::Error),
+}
+
+pub struct ManagedRepository {
+	pub path: PathBuf,
+	pub tracked_branches: Vec<String>,
+	pub upstream_remote_url: String,
+	pub upstream_remote_name: String,
+}
+
+impl ManagedRepository {
+	/// basic set of options for fetching from remotes
+	fn fetch_options<'a>() -> FetchOptions<'a> {
+		let mut remote_callbacks = RemoteCallbacks::new();
+		remote_callbacks.transfer_progress(|progress| {
+			if progress.received_objects() == progress.total_objects() {
+				trace!(
+					"Resolving deltas {}/{}\r",
+					progress.indexed_deltas(),
+					progress.total_deltas()
+				);
+			} else {
+				trace!(
+					"Received {}/{} objects ({}) in {} bytes\r",
+					progress.received_objects(),
+					progress.total_objects(),
+					progress.indexed_objects(),
+					progress.received_bytes()
+				);
+			}
+			std::io::stdout().flush().ok();
+			true
+		});
+
+		let mut fetch_opts = FetchOptions::new();
+		fetch_opts.remote_callbacks(remote_callbacks);
+
+		fetch_opts
+	}
+
+	/// Update the given branches in the [`repository`] using the nixpkgs remote
+	fn update_branches_in(&self, repository: &Repository) -> Result<(), Error> {
+		let mut remote = repository.find_remote(&self.upstream_remote_name)?;
+		// download all the refs
+		remote.download(&self.tracked_branches, Some(&mut Self::fetch_options()))?;
+		remote.disconnect()?;
+		// and (hopefully) update what they refer to for later
+		remote.update_tips(
+			None,
+			RemoteUpdateFlags::UPDATE_FETCHHEAD,
+			AutotagOption::Auto,
+			None,
+		)?;
+
+		Ok(())
+	}
+
+	/// Fetch the repository or update it if it exists
+	///
+	/// # Errors
+	/// Will return [`Err`] if the repository cannot be opened, cloned, or updated
+	pub fn fetch_or_update(&self) -> Result<(), Error> {
+		// Open our repository or clone it if it doesn't exist
+		let repository = if self.path.exists() {
+			Repository::open(self.path.as_path())?
+		} else {
+			warn!(
+				"Couldn't find repository at {}! Cloning a fresh one from {}",
+				self.path.display(),
+				self.upstream_remote_url
+			);
+			Repository::clone(&self.upstream_remote_url, self.path.as_path())?;
+			info!("Finished cloning to {}", self.path.display());
+
+			// bail early as we already have a fresh copy
+			return Ok(());
+		};
+
+		debug!("Updating repository at {}", self.path.display());
+		self.update_branches_in(&repository)?;
+		debug!("Finished updating!");
+
+		Ok(())
+	}
+}