[TESTS] Add comprehensive tests for parse_update_entry function

Summary

The parse_update_entry function in src/util/mod.rs parses update lines but could benefit from more comprehensive tests covering edge cases. Add tests for malformed input, package names with dashes, empty/whitespace input, and Unicode characters.

Files to modify

• src/util/mod.rs (add test cases in the #[cfg(test)] module)

Expected behavior

The test suite should cover:

1. Valid inputs: Standard pacman update format parsing
2. Malformed inputs: Missing arrows, malformed versions, incomplete entries
3. Edge cases: Package names with dashes, empty/whitespace input, Unicode characters
4. Error handling: Proper None returns for invalid formats

Implementation approach

Add a new test function util_parse_update_entry with comprehensive test cases:

Testing

• cargo check passes
• cargo clippy --all-targets --all-features -- -D warnings passes
• cargo test -- --test-threads=1 passes
• Test valid parsing of standard pacman update format
• Test malformed inputs return None
• Test package names containing dashes are handled correctly
• Test empty and whitespace-only inputs return None
• Test Unicode characters in package names
• Test version numbers with various formats (numbers, letters, dashes)
• Test edge cases with extra whitespace around separators

Additional context

The parse_update_entry function parses lines in the format:

"name - old_version -> name - new_version"

Key parsing logic:

• Uses find(" -> ") to locate the arrow separator
• Uses rfind(" - ") to find the last dash before the arrow (handles package names with dashes)
• Returns None for any malformed input

Test cases should cover real-world pacman output scenarios and ensure the function is robust against various input formats and edge cases that might occur in practice.