fix(git): show branch name in fresh repo (unborn master) (#1093)

* fix: branch_name in fresh repo (unborn master)

* test: add test for unborn branch_name fix

src/context.rs

@@ -3,7 +3,7 @@ use crate::module::Module;
 
 use crate::modules;
 use clap::ArgMatches;
-use git2::{Repository, RepositoryState};
+use git2::{ErrorCode::UnbornBranch, Repository, RepositoryState};
 use once_cell::sync::OnceCell;
 use std::collections::{HashMap, HashSet};
 use std::env;
@@ -312,7 +312,19 @@ impl<'a> ScanDir<'a> {
 }
 
 fn get_current_branch(repository: &Repository) -> Option<String> {
-    let head = repository.head().ok()?;
+    let head = match repository.head() {
+        Ok(reference) => reference,
+        Err(e) => {
+            return if e.code() == UnbornBranch {
+                // HEAD should only be an unborn branch if the repository is fresh,
+                // in that case assume "master"
+                Some(String::from("master"))
+            } else {
+                None
+            };
+        }
+    };
+
     let shorthand = head.shorthand();
 
     shorthand.map(std::string::ToString::to_string)

tests/testsuite/git_branch.rs

@@ -98,6 +98,30 @@ fn test_japanese_truncation() -> io::Result<()> {
     test_truncate_length("がんばってね", 4, "がんばっ", "…")
 }
 
+#[test]
+fn test_works_with_unborn_master() -> io::Result<()> {
+    let repo_dir = tempfile::tempdir()?.into_path();
+
+    Command::new("git")
+        .args(&["init"])
+        .current_dir(&repo_dir)
+        .output()?;
+
+    let output = common::render_module("git_branch")
+        .arg("--path")
+        .arg(&repo_dir)
+        .output()
+        .unwrap();
+    let actual = String::from_utf8(output.stdout).unwrap();
+
+    let expected = format!(
+        "on {} ",
+        Color::Purple.bold().paint(format!("\u{e0a0} {}", "master")),
+    );
+    assert_eq!(expected, actual);
+    remove_dir_all(repo_dir)
+}
+
 fn test_truncate_length(
     branch_name: &str,
     truncate_length: i64,