Add RUSTSEC advisory for git2 (#2620)

Author: BoLu1225

crates/git2/RUSTSEC-0000-0000.md

@@ -0,0 +1,17 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "git2"
+date = "2026-02-02"
+url = "https://github.com/rust-lang/git2-rs/pull/1213"
+informational = "unsound"
+categories = ["memory-corruption"]
+keywords = ["undefined-behavior"]
+
+[versions]
+patched = [">=0.20.4"]
+```
+# Potential undefined behavior when dereferencing Buf struct 
+
+if we dereference the Buf struct right after calling new() or default() on Buf struct, it passes Null Pointer to the unsafe function slice::from_raw_parts. Based on the safety section documentation of function,
+data must be non-null and aligned even for zero-length slices or slices of ZSTs. Thus, passing Null Pointer will lead to undefined behavior.