step twenty one: tag, generalize HEAD to refs

src/base.rs

@@ -71,7 +71,7 @@ pub fn read_tree(oid: String) {
 pub fn commit(message: &str) -> String {
     let mut commit = format!("tree {}\n", write_tree(".".to_owned()));
 
-    if let Ok(head) = data::get_head() {
+    if let Ok(head) = data::get_ref("HEAD".to_owned()) {
         commit += format!("parent {}\n", head).as_str();
     }
 
@@ -79,7 +79,7 @@ pub fn commit(message: &str) -> String {
     commit += format!("{}\n", message).as_str();
 
     let oid = data::hash_object(&commit.into_bytes(), "commit".to_owned());
-    data::set_head(oid.clone());
+    data::update_ref("HEAD".to_owned(), oid.clone());
     return oid;
 }
 
@@ -112,7 +112,7 @@ pub fn get_commit(oid: String) -> Commit {
 pub fn checkout(oid: String) {
     let commit = get_commit(oid.clone());
     read_tree(commit.tree);
-    data::set_head(oid);
+    data::update_ref("HEAD".to_owned(), oid);
 }
 
 pub fn create_tag(name: String, oid: String) {

src/data.rs

@@ -42,11 +42,11 @@ pub fn get_object(hash: String, expected: String) -> String {
     return data;
 }
 
-pub fn set_head(oid: String) {
+pub fn update_ref(reference: String, oid: String) {
-    fs::write(format!("{}/HEAD", RGIT_DIR), oid).expect("Failed to updated HEAD");
+    fs::write(format!("{}/{}", RGIT_DIR, reference), oid).expect("Failed to updated HEAD");
 }
 
-pub fn get_head() -> Result<String, Box<dyn std::error::Error + 'static>> {
+pub fn get_ref(reference: String) -> Result<String, Box<dyn std::error::Error + 'static>> {
-    let oid = fs::read_to_string(format!("{}/HEAD", RGIT_DIR))?;
+    let oid = fs::read_to_string(format!("{}/{}", RGIT_DIR, reference))?;
     return Ok(oid);
 }

src/main.rs

@@ -119,7 +119,7 @@ fn log_commits(matches: ArgMatches) {
         let provided_oid = cmd_matches.value_of("oid").unwrap_or("");
         let mut oid;
         if provided_oid == "" {
-            oid = data::get_head().expect("Cannot read HEAD file");
+            oid = data::get_ref("HEAD".to_owned()).expect("Cannot read HEAD file");
         } else {
             oid = provided_oid.to_owned();
         }
@@ -152,7 +152,7 @@ fn tag(matches: ArgMatches) {
         let name = cmd_matches.value_of("name").unwrap().to_owned();
         let mut oid = cmd_matches.value_of("oid").unwrap_or("").to_owned();
         if oid == "" {
-            oid = data::get_head().expect("Cannot read HEAD");
+            oid = data::get_ref("HEAD".to_owned()).expect("Cannot read HEAD");
         }
         base::create_tag(name, oid);
     }