Fix annotated tag OID to canonical hash of serialized form
Tag::new previously hashed a Display-based string instead of to_data(),
so id != hash(to_data()), breaking packfile round-trips of annotated
tags. Hash to_data() to keep the id canonical, add regression test, and
bump version to 0.7.6.
Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com
Signed-off-by: Eli Ma eli@patch.sh