fix(stash): improve error message specificity in stash parsing

- Include expected and actual parts count in validation error message
- Add validation for empty remainder part containing branch and message
- Add comprehensive test coverage for parsing edge cases
- Change from generic "Invalid format" to specific "expected 4 parts, got X"

Author: eugener

src/commands/stash.rs

@@ -491,9 +491,10 @@ fn parse_stash_line(index: usize, line: &str) -> Result<Stash> {
     let parts: Vec<&str> = line.splitn(4, ' ').collect();
 
     if parts.len() < 4 {
-        return Err(GitError::CommandFailed(
-            "Invalid stash list format".to_string(),
-        ));
+        return Err(GitError::CommandFailed(format!(
+            "Invalid stash list format: expected 4 parts, got {}",
+            parts.len()
+        )));
     }
 
     let hash = Hash::from(parts[1]);
@@ -503,6 +504,12 @@ fn parse_stash_line(index: usize, line: &str) -> Result<Stash> {
 
     // Extract branch name and message from parts[3] (should be "On branch: message")
     let remainder = parts[3];
+    if remainder.is_empty() {
+        return Err(GitError::CommandFailed(
+            "Invalid stash format: missing branch and message information".to_string(),
+        ));
+    }
+
     let (branch, message) = if let Some(colon_pos) = remainder.find(':') {
         let branch_part = &remainder[..colon_pos];
         let message_part = &remainder[colon_pos + 1..].trim();
@@ -795,4 +802,48 @@ mod tests {
         assert!(display_str.contains("stash@{0}"));
         assert!(display_str.contains("Test stash message"));
     }
+
+    #[test]
+    fn test_parse_stash_line_invalid_format() {
+        // Test with insufficient parts
+        let invalid_line = "stash@{0} abc123"; // Only 2 parts instead of 4
+        let result = parse_stash_line(0, invalid_line);
+
+        assert!(result.is_err());
+        if let Err(GitError::CommandFailed(msg)) = result {
+            assert!(msg.contains("Invalid stash list format"));
+            assert!(msg.contains("expected 4 parts"));
+            assert!(msg.contains("got 2"));
+        } else {
+            panic!("Expected CommandFailed error with specific message");
+        }
+    }
+
+    #[test]
+    fn test_parse_stash_line_empty_remainder() {
+        // Test with empty remainder part
+        let invalid_line = "stash@{0} abc123 1234567890 "; // Empty 4th part
+        let result = parse_stash_line(0, invalid_line);
+
+        assert!(result.is_err());
+        if let Err(GitError::CommandFailed(msg)) = result {
+            assert!(msg.contains("missing branch and message information"));
+        } else {
+            panic!("Expected CommandFailed error for empty remainder");
+        }
+    }
+
+    #[test]
+    fn test_parse_stash_line_valid_format() {
+        // Test with valid format
+        let valid_line = "stash@{0} abc123def456 1234567890 On master: test message";
+        let result = parse_stash_line(0, valid_line);
+
+        assert!(result.is_ok());
+        let stash = result.unwrap();
+        assert_eq!(stash.index, 0);
+        assert_eq!(stash.hash.as_str(), "abc123def456");
+        assert_eq!(stash.branch, "master");
+        assert_eq!(stash.message, "test message");
+    }
 }