feat: add ecc2 worktree file previews

ecc2/src/worktree/mod.rs

@@ -107,6 +107,35 @@ pub fn diff_summary(worktree: &WorktreeInfo) -> Result<Option<String>> {
     }
 }
 
+pub fn diff_file_preview(worktree: &WorktreeInfo, limit: usize) -> Result<Vec<String>> {
+    let mut preview = Vec::new();
+    let base_ref = format!("{}...HEAD", worktree.base_branch);
+
+    let committed = git_diff_name_status(&worktree.path, &[&base_ref])?;
+    if !committed.is_empty() {
+        preview.extend(
+            committed
+                .into_iter()
+                .map(|entry| format!("Branch {entry}"))
+                .take(limit.saturating_sub(preview.len())),
+        );
+    }
+
+    if preview.len() < limit {
+        let working = git_status_short(&worktree.path)?;
+        if !working.is_empty() {
+            preview.extend(
+                working
+                    .into_iter()
+                    .map(|entry| format!("Working {entry}"))
+                    .take(limit.saturating_sub(preview.len())),
+            );
+        }
+    }
+
+    Ok(preview)
+}
+
 fn git_diff_shortstat(worktree_path: &Path, extra_args: &[&str]) -> Result<Option<String>> {
     let mut command = Command::new("git");
     command
@@ -137,6 +166,60 @@ fn git_diff_shortstat(worktree_path: &Path, extra_args: &[&str]) -> Result<Optio
     }
 }
 
+fn git_diff_name_status(worktree_path: &Path, extra_args: &[&str]) -> Result<Vec<String>> {
+    let mut command = Command::new("git");
+    command
+        .arg("-C")
+        .arg(worktree_path)
+        .arg("diff")
+        .arg("--name-status");
+    command.args(extra_args);
+
+    let output = command
+        .output()
+        .context("Failed to generate worktree diff file preview")?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        tracing::warn!(
+            "Worktree diff file preview warning for {}: {stderr}",
+            worktree_path.display()
+        );
+        return Ok(Vec::new());
+    }
+
+    Ok(parse_nonempty_lines(&output.stdout))
+}
+
+fn git_status_short(worktree_path: &Path) -> Result<Vec<String>> {
+    let output = Command::new("git")
+        .arg("-C")
+        .arg(worktree_path)
+        .args(["status", "--short"])
+        .output()
+        .context("Failed to generate worktree status preview")?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        tracing::warn!(
+            "Worktree status preview warning for {}: {stderr}",
+            worktree_path.display()
+        );
+        return Ok(Vec::new());
+    }
+
+    Ok(parse_nonempty_lines(&output.stdout))
+}
+
+fn parse_nonempty_lines(stdout: &[u8]) -> Vec<String> {
+    String::from_utf8_lossy(stdout)
+        .lines()
+        .map(str::trim)
+        .filter(|line| !line.is_empty())
+        .map(ToOwned::to_owned)
+        .collect()
+}
+
 fn get_current_branch(repo_root: &Path) -> Result<String> {
     let output = Command::new("git")
         .arg("-C")
@@ -157,7 +240,11 @@ mod tests {
     use uuid::Uuid;
 
     fn run_git(repo: &Path, args: &[&str]) -> Result<()> {
-        let output = Command::new("git").arg("-C").arg(repo).args(args).output()?;
+        let output = Command::new("git")
+            .arg("-C")
+            .arg(repo)
+            .args(args)
+            .output()?;
         if !output.status.success() {
             anyhow::bail!("{}", String::from_utf8_lossy(&output.stderr));
         }
@@ -196,7 +283,10 @@ mod tests {
             base_branch: "main".to_string(),
         };
 
-        assert_eq!(diff_summary(&info)?, Some("Clean relative to main".to_string()));
+        assert_eq!(
+            diff_summary(&info)?,
+            Some("Clean relative to main".to_string())
+        );
 
         fs::write(worktree_dir.join("README.md"), "hello\nmore\n")?;
         let dirty = diff_summary(&info)?.expect("dirty summary");
@@ -212,4 +302,63 @@ mod tests {
         let _ = fs::remove_dir_all(root);
         Ok(())
     }
+
+    #[test]
+    fn diff_file_preview_reports_branch_and_working_tree_files() -> Result<()> {
+        let root = std::env::temp_dir().join(format!("ecc2-worktree-preview-{}", Uuid::new_v4()));
+        let repo = root.join("repo");
+        fs::create_dir_all(&repo)?;
+
+        run_git(&repo, &["init", "-b", "main"])?;
+        run_git(&repo, &["config", "user.email", "ecc@example.com"])?;
+        run_git(&repo, &["config", "user.name", "ECC"])?;
+        fs::write(repo.join("README.md"), "hello\n")?;
+        run_git(&repo, &["add", "README.md"])?;
+        run_git(&repo, &["commit", "-m", "init"])?;
+
+        let worktree_dir = root.join("wt-1");
+        run_git(
+            &repo,
+            &[
+                "worktree",
+                "add",
+                "-b",
+                "ecc/test",
+                worktree_dir.to_str().expect("utf8 path"),
+                "HEAD",
+            ],
+        )?;
+
+        fs::write(worktree_dir.join("src.txt"), "branch\n")?;
+        run_git(&worktree_dir, &["add", "src.txt"])?;
+        run_git(&worktree_dir, &["commit", "-m", "branch file"])?;
+        fs::write(worktree_dir.join("README.md"), "hello\nworking\n")?;
+
+        let info = WorktreeInfo {
+            path: worktree_dir.clone(),
+            branch: "ecc/test".to_string(),
+            base_branch: "main".to_string(),
+        };
+
+        let preview = diff_file_preview(&info, 6)?;
+        assert!(
+            preview
+                .iter()
+                .any(|line| line.contains("Branch A") && line.contains("src.txt"))
+        );
+        assert!(
+            preview
+                .iter()
+                .any(|line| line.contains("Working M") && line.contains("README.md"))
+        );
+
+        let _ = Command::new("git")
+            .arg("-C")
+            .arg(&repo)
+            .args(["worktree", "remove", "--force"])
+            .arg(&worktree_dir)
+            .output();
+        let _ = fs::remove_dir_all(root);
+        Ok(())
+    }
 }