Add CLI command to list Git-style references

[jordpo]

Summary

Implements a new icechunk ref list command that displays all branches and tags in an Icechunk repository, providing Git-style reference listing functionality from the CLI.

Fixes #827

Motivation

Users need a convenient way to view all references (branches and tags) in their Icechunk repositories from the command line, similar to git show-ref or git branch -a. Currently, this requires using the Python API, which is less convenient for quick repository inspection.

Approach

This PR adds a new ref subcommand to the Icechunk CLI with a list operation that:

1. Follows existing patterns: Implemented similarly to existing commands like snapshot list and config list
2. Leverages existing APIs: Uses Repository::list_branches() and Repository::list_tags() methods that are already available in the Rust codebase
3. Clean output format: Displays references in a clear format:

   branch: main
   branch: feature
   tag: v1.0
   

Changes

• Added Ref(RefCommand) variant to the CLI Command enum
• Created RefCommand enum with List(RefListCommand) subcommand
• Implemented ref_list() handler function that:
  • Opens the repository from config
  • Retrieves all branches and tags
  • Formats output with clear labels
• Wired up the command in the run_cli() executor
• Added comprehensive test coverage

Test Coverage

Added test_ref_list() integration test that:

• Creates a test repository with the main branch
• Adds an additional branch (feature) and tag (v1.0)
• Verifies all references appear in the output
• Validates output format and line count

Test passes with:

cargo test --lib --features cli cli::interface::tests::test_ref_list

Usage

# List all references in a repository
icechunk ref list <repository-alias>

# Example output:
# branch: main
# branch: feature-x
# tag: v1.0.0
# tag: v2.0.0-beta

Testing

Manually tested with:

cargo build --features cli
./target/debug/icechunk ref --help
./target/debug/icechunk ref list --help

All existing CLI tests continue to pass.

🤖 Generated with Claude Code