add expected_current_target

lib/src/git.rs

@@ -1226,9 +1226,8 @@ pub struct GitBranchPushTargets {
 
 pub struct GitRefUpdate {
     pub qualified_name: String,
-    // TODO: We want this to be a `current_target: Option<CommitId>` for the expected current
-    // commit on the remote. It's a blunt "force" option instead until git2-rs supports the
-    // "push negotiation" callback (https://github.com/rust-lang/git2-rs/issues/733).
+    pub expected_current_target: Option<CommitId>,
+    // Short-term TODO: Delete `force`
     pub force: bool,
     pub new_target: Option<CommitId>,
 }
@@ -1247,6 +1246,7 @@ pub fn push_branches(
         .map(|(branch_name, update)| GitRefUpdate {
             qualified_name: format!("refs/heads/{branch_name}"),
             force: targets.force_pushed_branches.contains(branch_name),
+            expected_current_target: update.old_target.clone(),
             new_target: update.new_target.clone(),
         })
         .collect_vec();

lib/tests/test_git.rs

@@ -2774,6 +2774,7 @@ fn test_push_updates_success() {
         &[GitRefUpdate {
             qualified_name: "refs/heads/main".to_string(),
             force: false,
+            expected_current_target: Some(setup.initial_commit.id().clone()),
             new_target: Some(setup.new_commit.id().clone()),
         }],
         git::RemoteCallbacks::default(),
@@ -2810,6 +2811,7 @@ fn test_push_updates_no_such_remote() {
         &[GitRefUpdate {
             qualified_name: "refs/heads/main".to_string(),
             force: false,
+            expected_current_target: Some(setup.initial_commit.id().clone()),
             new_target: Some(setup.new_commit.id().clone()),
         }],
         git::RemoteCallbacks::default(),
@@ -2828,6 +2830,7 @@ fn test_push_updates_invalid_remote() {
         &[GitRefUpdate {
             qualified_name: "refs/heads/main".to_string(),
             force: false,
+            expected_current_target: Some(setup.initial_commit.id().clone()),
             new_target: Some(setup.new_commit.id().clone()),
         }],
         git::RemoteCallbacks::default(),