1 files changed, 53 insertions, 0 deletions
diff --git a/src/util.rs b/src/util.rs
index a829327..5394fb0 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -130,6 +130,59 @@ pub fn print_collected_packages(packages: &PackageList, message: &str) {
     );
 }
 
+pub fn pull_latest_tag(path: &Path) -> Result<(), git2::Error> {
+    let repo = Repository::open(path)?;
+
+    let head = repo.head()?;
+    let branch = head
+        .shorthand()
+        .ok_or_else(|| git2::Error::from_str("Could not determine current branch"))?
+        .to_string();
+
+    let mut callbacks = RemoteCallbacks::new();
+    callbacks.credentials(|_url, username_from_url, _allowed| {
+        Cred::ssh_key_from_agent(username_from_url.unwrap())
+    });
+
+    let mut fetch_options = FetchOptions::new();
+    fetch_options.remote_callbacks(callbacks);
+
+    let mut remote = repo.find_remote("origin")?;
+    remote.fetch(&["refs/tags/*:refs/tags/*"], Some(&mut fetch_options), None)?;
+
+    let tag_names = repo.tag_names(None)?;
+
+    let mut latest_commit = None;
+    let mut latest_time = 0;
+
+    for name in tag_names.iter().flatten() {
+        let obj = repo.revparse_single(&format!("refs/tags/{}", name))?;
+        let commit = obj.peel_to_commit()?;
+
+        let time = commit.time().seconds();
+        if time > latest_time {
+            latest_time = time;
+            latest_commit = Some(commit);
+        }
+    }
+
+    let latest_commit = latest_commit.ok_or_else(|| git2::Error::from_str("No tags found"))?;
+
+    let annotated = repo.find_annotated_commit(latest_commit.id())?;
+    let (analysis, _) = repo.merge_analysis(&[&annotated])?;
+
+    if analysis.is_fast_forward() {
+        let refname = format!("refs/heads/{}", branch);
+        let mut reference = repo.find_reference(&refname)?;
+        reference.set_target(latest_commit.id(), "Fast-Forward to latest tag")?;
+        repo.set_head(&refname)?;
+        repo.checkout_head(Some(CheckoutBuilder::default().force()))?;
+    } else if !analysis.is_up_to_date() {
+        println!("Cannot fast-forward to latest tag.");
+    }
+
+    Ok(())
+}
 pub fn pull_repo(path: &Path) -> Result<(), git2::Error> {
     let repo = Repository::open(path)?;