feat: spawn concurrent list-repo tasks

Concurrently lookup repositories when caling "list_repos". Because I'm
really not an async Rust expert, there's a bunch of unsafe code to allow
for immutable references to Self. Avoiding those would be awesome, but
even with the unsafe trickery, the speed-up is insane:
instead of listing 30 repos with a response time of ~100ms sequentially,
we make 30 responses in parallel, which only takes a couple hundred ms
in total!

src/remote/gitea.rs

@@ -1,6 +1,9 @@
 use crate::error::{Error, ErrorKind, Result};
 use async_trait::async_trait;
-use teatime::{error::{TeatimeError, TeatimeErrorKind}, Client, CreateRepoOption, GetCommitsOption};
+use teatime::{
+    error::{TeatimeError, TeatimeErrorKind},
+    Client, CreateRepoOption, GetCommitsOption,
+};
 
 use super::*;
 
@@ -61,9 +64,16 @@ impl Remote for GiteaRemote {
             ..Default::default()
         };
         let repos = self.client.search_repositories(&search_option).await?;
-        let mut result = Vec::new();
+        let mut futures = Vec::new();
         for repo in repos {
-            result.push(self.get_repo_info(repo).await?);
+            // SAFETY: We are not moving `self` in the closure, self is guaranteed to be valid as
+            // long as the closure is running and we're not mutating it, so this is safe.
+            let this = unsafe { &*(self as *const Self) };
+            futures.push(tokio::spawn((*this).get_repo_info(repo)));
+        }
+        let mut result = Vec::with_capacity(futures.len());
+        for future in futures {
+            result.push(future.await.unwrap()?);
         }
         Ok(result)
     }
@@ -75,7 +85,8 @@ impl Remote for GiteaRemote {
     }
 
     async fn delete_repo(&self, name: &str) -> Result<()> {
-        Ok(self.client
+        Ok(self
+            .client
             .delete_repository(&self.config.username, name)
             .await?)
     }

src/remote/github.rs

@@ -113,20 +113,33 @@ impl Remote for GitHubRemote {
             .order("desc")
             .send()
             .await?;
-        let mut result = Vec::new();
+        let mut futures = Vec::new();
         for repo in repos {
-            let base = self
+            // SAFETY: We are not moving `self` in the closure, self is guaranteed to be valid as
+            // long as the closure is running and we're not mutating it, so this is safe.
+            let this = unsafe { &*(self as *const Self) };
+            let base = this
                 .crab
                 .repos(self.config.username.clone(), repo.name.clone());
-            result.push(self.get_repo_info(base, repo).await?);
+            let username = &self.config.username;
+            futures.push(tokio::spawn(Self::get_repo_info(
+                username.clone(),
+                base,
+                repo,
+            )));
+        }
+        let mut result = Vec::with_capacity(futures.len());
+        for future in futures {
+            let f = future.await.unwrap()?;
+            result.push(f);
         }
         Ok(result)
     }
 
     async fn get_repo_info(&self, name: &str) -> Result<Repository> {
         let base = self.crab.repos(self.config.username.clone(), name);
         let repo = base.get().await?;
-        self.get_repo_info(base, repo).await
+        Self::get_repo_info(self.config.username.clone(), base, repo).await
     }
 
     async fn delete_repo(&self, name: &str) -> Result<()> {
@@ -141,11 +154,10 @@ impl Remote for GitHubRemote {
 
 impl GitHubRemote {
     async fn get_repo_info(
-        &self,
+        username: String,
         base: RepoHandler<'_>,
         repo: models::Repository,
     ) -> Result<Repository> {
-        let username = &self.config.username;
         let commits = base
             .list_commits()
             .per_page(super::COMMIT_COUNT)