git remote rename: rename git refs as well

CHANGELOG.md

@@ -37,6 +37,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj git fetch`: when re-adding a remote repository that had been previously
   removed, in some situations the remote branches were not recreated.
 
+* `jj git remote rename`: the git remote references were not rewritten with
+  the new name. If a new remote with the old name and containing the same
+  branches was added, the remote branches may not be recreated in some cases.
+
 ## [0.7.0] - 2023-02-16
 
 ### Breaking changes

src/commands/git.rs

@@ -230,6 +230,28 @@ fn cmd_git_remote_rename(
     let mut tx = workspace_command
         .start_transaction(&format!("rename git remote {} to {}", &args.old, &args.new));
     tx.mut_repo().rename_remote(&args.old, &args.new);
+
+    let prefix = format!("refs/remotes/{}/", args.old);
+    let git_refs = tx
+        .mut_repo()
+        .view()
+        .git_refs()
+        .iter()
+        .filter_map(|(r, target)| {
+            r.strip_prefix(&prefix).map(|p| {
+                (
+                    r.clone(),
+                    format!("refs/remotes/{}/{p}", args.new),
+                    target.clone(),
+                )
+            })
+        })
+        .collect_vec();
+    for (old, new, target) in git_refs {
+        tx.mut_repo().remove_git_ref(&old);
+        tx.mut_repo().set_git_ref(new, target);
+    }
+
     if tx.mut_repo().has_changes() {
         tx.finish(ui)?;
     }

tests/test_git_fetch.rs

@@ -705,3 +705,41 @@ fn test_git_fetch_remove_fetch() {
       @origin (behind by 1 commits): ffecd2d67827 message
     "###);
 }
+
+#[test]
+fn test_git_fetch_rename_fetch() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+    add_git_remote(&test_env, &repo_path, "origin");
+
+    test_env.jj_cmd_success(&repo_path, &["branch", "set", "origin"]);
+    insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
+    origin: 230dd059e1b0 (no description set)
+    "###);
+
+    test_env.jj_cmd_success(&repo_path, &["git", "fetch"]);
+    insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
+    origin (conflicted):
+      + 230dd059e1b0 (no description set)
+      + ffecd2d67827 message
+      @origin (behind by 1 commits): ffecd2d67827 message
+    "###);
+
+    test_env.jj_cmd_success(
+        &repo_path,
+        &["git", "remote", "rename", "origin", "upstream"],
+    );
+    insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
+    origin (conflicted):
+      + 230dd059e1b0 (no description set)
+      + ffecd2d67827 message
+      @upstream (behind by 1 commits): ffecd2d67827 message
+    "###);
+
+    // Check that jj indicates that nothing has changed
+    let stdout = test_env.jj_cmd_success(&repo_path, &["git", "fetch", "--remote", "upstream"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Nothing changed.
+    "###);
+}