wip!: orphan branch with initial commit for variant

the initial commit will house metadata on the variant
that is being derived like the author, the configs and
so on.

Author: oahshtsua

src/lib.rs

@@ -1,5 +1,5 @@
 use anyhow::{Context, Result};
-use git2::{BranchType, Commit, Repository, Sort};
+use git2::{BranchType, Commit, Repository, Signature, Sort};
 use regex::Regex;
 use std::fs;
 use std::io::Write;
@@ -42,6 +42,28 @@ pub fn init(repo: &Repository) -> Result<()> {
 pub fn derive(repo: &Repository, name: &str, features: &[String]) -> Result<()> {
     println!("Deriving variant '{}' with features: {:?}", name, features);
     // create a new orphan branch
+    let tree_oid = repo
+        .treebuilder(None)?
+        .write()
+        .context("Failed to create empty tree.")?;
+    let tree = repo.find_tree(tree_oid)?;
+    println!("Treeid: {:?}", tree_oid);
+
+    let sig = Signature::now("user", "user@example.com")?;
+
+    let ref_name = format!("refs/heads/variant/{name}");
+    let commit_oid = repo
+        .commit(
+            Some(&ref_name),
+            &sig,
+            &sig,
+            "Variant initial commit\n",
+            &tree,
+            &[],
+        )
+        .context("Failed to create initial commit for variant")?;
+    println!("Commit id: {:?}", commit_oid);
+
     // walk the commit graph
     let mut revwalk = repo.revwalk()?;
     revwalk.push_head()?;