agent2: Initial infra for checkpoints and message editing (#36120)

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>

crates/git/Cargo.toml

@@ -12,7 +12,7 @@ workspace = true
 path = "src/git.rs"
 
 [features]
-test-support = []
+test-support = ["rand"]
 
 [dependencies]
 anyhow.workspace = true
@@ -26,6 +26,7 @@ http_client.workspace = true
 log.workspace = true
 parking_lot.workspace = true
 regex.workspace = true
+rand = { workspace = true, optional = true }
 rope.workspace = true
 schemars.workspace = true
 serde.workspace = true
@@ -47,3 +48,4 @@ text = { workspace = true, features = ["test-support"] }
 unindent.workspace = true
 gpui = { workspace = true, features = ["test-support"] }
 tempfile.workspace = true
+rand.workspace = true

crates/git/src/git.rs

@@ -119,6 +119,13 @@ impl Oid {
         Ok(Self(oid))
     }
 
+    #[cfg(any(test, feature = "test-support"))]
+    pub fn random(rng: &mut impl rand::Rng) -> Self {
+        let mut bytes = [0; 20];
+        rng.fill(&mut bytes);
+        Self::from_bytes(&bytes).unwrap()
+    }
+
     pub fn as_bytes(&self) -> &[u8] {
         self.0.as_bytes()
     }