step fifty three: three way merge

src/base.rs

@@ -284,6 +284,8 @@ pub fn merge(oid: String) {
     let head = data::get_ref("HEAD".to_owned(), true);
     assert!(head.value != "");
 
+    let merge_base = get_merge_base(oid.clone(), head.value.clone());
+    let c_base = get_commit(merge_base);
     let c_head = get_commit(head.value);
     let c_other = get_commit(oid.clone());
 
@@ -296,7 +298,7 @@ pub fn merge(oid: String) {
         true,
     );
 
-    read_tree_merged(c_head.tree, c_other.tree);
+    read_tree_merged(c_base.tree, c_head.tree, c_other.tree);
     println!("Merged in working tree");
     println!("Please commit");
 }
@@ -410,11 +412,12 @@ fn is_branch(name: String) -> bool {
     return data::get_ref(name, true).value != "";
 }
 
-fn read_tree_merged(head_tree: String, commit_tree: String) {
+fn read_tree_merged(base_tree: String, head_tree: String, commit_tree: String) {
     empty_current_directory(".").unwrap();
+    let base_tree = get_tree(base_tree, "".to_owned());
     let head_tree = get_tree(head_tree, "".to_owned());
     let commit_tree = get_tree(commit_tree, "".to_owned());
-    for (path, blob) in diff::merge_trees(head_tree, commit_tree) {
+    for (path, blob) in diff::merge_trees(base_tree, head_tree, commit_tree) {
         let mut dirs = Path::new(&path).ancestors();
         dirs.next();
 

src/diff.rs

@@ -91,19 +91,32 @@ pub fn changed_files(
     return result;
 }
 
-pub fn merge_trees(t_head: HashMap<String, String>, t_other: HashMap<String, String>) -> HashMap<String, String> {
+pub fn merge_trees(
+    t_base: HashMap<String, String>,
+    t_head: HashMap<String, String>,
+    t_other: HashMap<String, String>,
+) -> HashMap<String, String> {
     let mut tree = HashMap::new();
-    let trees = vec![t_head, t_other];
+    let trees = vec![t_base, t_head, t_other];
     for (path, oids) in compare_trees(trees).iter() {
-        tree.insert(path.clone(), merge_blobs(oids[0].clone(), oids[1].clone()));
+        tree.insert(
+            path.clone(),
+            merge_blobs(oids[0].clone(), oids[1].clone(), oids[2].clone()),
+        );
     }
     return tree;
 }
 
-fn merge_blobs(o_head: String, o_other: String) -> String {
+fn merge_blobs(o_base: String, o_head: String, o_other: String) -> String {
+    let f_base = NamedTempFile::new().unwrap();
     let f_head = NamedTempFile::new().unwrap();
     let f_other = NamedTempFile::new().unwrap();
 
+    if o_base != "" {
+        let content = data::get_object(o_base, "blob".to_owned());
+        fs::write(f_base.path(), content).unwrap();
+    }
+
     if o_head != "" {
         let content = data::get_object(o_head, "blob".to_owned());
         fs::write(f_head.path(), content).unwrap();
@@ -114,9 +127,16 @@ fn merge_blobs(o_head: String, o_other: String) -> String {
         fs::write(f_other.path(), content).unwrap();
     }
 
-    let output = Command::new("diff")
-        .arg("-DHEAD")
+    let output = Command::new("diff3")
+        .arg("-m")
+        .arg("-L")
+        .arg("HEAD")
         .arg(f_head.path())
+        .arg("-L")
+        .arg("BASE")
+        .arg(f_base.path())
+        .arg("-L")
+        .arg("MERGE_HEAD")
         .arg(f_other.path())
         .stdout(Stdio::piped())
         .output()