git: support SSH keys for authentication to GitHub

CHANGELOG.md

@@ -21,3 +21,4 @@ This is the first release of palisade!
 - TL;DR Rust document
 - GitHub Action support
 - Commentary across the project
+- Support using SSH keys for authentication to GitHub

src/git.rs

@@ -4,14 +4,22 @@ use git2::{Cred, RemoteCallbacks, Repository, Signature};
 /// Push all tags in the repo to the upstream origin.
 pub(crate) fn push_tag(repo: &Repository, token: &String, tag: &String) -> Result<()> {
     let mut callbacks = RemoteCallbacks::new();
-    callbacks.credentials(|_u, _username_from_url, _allowed_types| {
-        Cred::userpass_plaintext(&token, "")
+    callbacks.credentials(|_u, _username_from_url, allowed_types| {
+        if allowed_types.contains(git2::CredentialType::SSH_KEY) {
+            let user = "git";
+            git2::Cred::ssh_key_from_agent(user)
+        } else {
+            Cred::userpass_plaintext(&token, "")
+        }
     });
     let mut remote = repo.find_remote("origin")?;
     let mut po = git2::PushOptions::new();
     po.remote_callbacks(callbacks);
 
-    match remote.push(&[&format!("refs/tags/{}:refs/tags/{}", tag, tag)], Some(&mut po)) {
+    match remote.push(
+        &[&format!("refs/tags/{}:refs/tags/{}", tag, tag)],
+        Some(&mut po),
+    ) {
         Ok(_) => Ok(()),
         Err(why) => Err(anyhow!("git push error: {:?}", why)),
     }