cli: branch: on create/set/rename, assume deleted tracking local branch still exists

cli/src/commands/branch/create.rs

@@ -16,6 +16,7 @@ use clap::builder::NonEmptyStringValueParser;
 use jj_lib::object_id::ObjectId as _;
 use jj_lib::op_store::RefTarget;
 
+use super::has_tracked_remote_branches;
 use crate::cli_util::{CommandHelper, RevisionArg};
 use crate::command_error::{user_error_with_hint, CommandError};
 use crate::ui::Ui;
@@ -42,14 +43,22 @@ pub fn cmd_branch_create(
         workspace_command.resolve_single_rev(args.revision.as_ref().unwrap_or(&RevisionArg::AT))?;
     let view = workspace_command.repo().view();
     let branch_names = &args.names;
-    if let Some(branch_name) = branch_names
-        .iter()
-        .find(|&name| view.get_local_branch(name).is_present())
-    {
-        return Err(user_error_with_hint(
-            format!("Branch already exists: {branch_name}"),
-            "Use `jj branch set` to update it.",
-        ));
+    for name in branch_names {
+        if view.get_local_branch(name).is_present() {
+            return Err(user_error_with_hint(
+                format!("Branch already exists: {name}"),
+                "Use `jj branch set` to update it.",
+            ));
+        }
+        if has_tracked_remote_branches(view, name) {
+            return Err(user_error_with_hint(
+                format!("Tracked remote branches exist for deleted branch: {name}"),
+                format!(
+                    "Use `jj branch set` to recreate the local branch. Run `jj branch untrack \
+                     'glob:{name}@*'` to disassociate them."
+                ),
+            ));
+        }
     }
 
     if branch_names.len() > 1 {

cli/src/commands/branch/mod.rs

@@ -159,6 +159,13 @@ fn find_remote_branches<'a>(
     }
 }
 
+/// Whether or not the `branch` has any tracked remotes (i.e. is a tracking
+/// local branch.)
+fn has_tracked_remote_branches(view: &View, branch: &str) -> bool {
+    view.remote_branches_matching(&StringPattern::exact(branch), &StringPattern::everything())
+        .any(|(_, remote_ref)| remote_ref.is_tracking())
+}
+
 fn is_fast_forward(repo: &dyn Repo, old_target: &RefTarget, new_target_id: &CommitId) -> bool {
     if old_target.is_present() {
         // Strictly speaking, "all" old targets should be ancestors, but we allow

cli/src/commands/branch/rename.rs

@@ -13,8 +13,8 @@
 // limitations under the License.
 
 use jj_lib::op_store::RefTarget;
-use jj_lib::str_util::StringPattern;
 
+use super::has_tracked_remote_branches;
 use crate::cli_util::CommandHelper;
 use crate::command_error::{user_error, CommandError};
 use crate::ui::Ui;
@@ -57,24 +57,31 @@ pub fn cmd_branch_rename(
     tx.finish(ui, format!("rename branch {old_branch} to {new_branch}"))?;
 
     let view = workspace_command.repo().view();
-    if view
-        .remote_branches_matching(
-            &StringPattern::exact(old_branch),
-            &StringPattern::everything(),
-        )
-        .any(|(_, remote_ref)| remote_ref.is_tracking())
-    {
+    if has_tracked_remote_branches(view, old_branch) {
         writeln!(
             ui.warning_default(),
-            "Branch {old_branch} has tracking remote branches which were not renamed."
+            "Tracked remote branches for branch {old_branch} were not renamed.",
         )?;
         writeln!(
             ui.hint_default(),
-            "to rename the branch on the remote, you can `jj git push --branch {old_branch}` \
+            "To rename the branch on the remote, you can `jj git push --branch {old_branch}` \
              first (to delete it on the remote), and then `jj git push --branch {new_branch}`. \
              `jj git push --all` would also be sufficient."
         )?;
     }
+    if has_tracked_remote_branches(view, new_branch) {
+        // This isn't an error because branch renaming can't be propagated to
+        // the remote immediately. "rename old new && rename new old" should be
+        // allowed even if the original old branch had tracked remotes.
+        writeln!(
+            ui.warning_default(),
+            "Tracked remote branches for branch {new_branch} exist."
+        )?;
+        writeln!(
+            ui.hint_default(),
+            "Run `jj branch untrack 'glob:{new_branch}@*'` to disassociate them."
+        )?;
+    }
 
     Ok(())
 }

cli/src/commands/branch/set.rs

@@ -16,7 +16,7 @@ use clap::builder::NonEmptyStringValueParser;
 use jj_lib::object_id::ObjectId as _;
 use jj_lib::op_store::RefTarget;
 
-use super::is_fast_forward;
+use super::{has_tracked_remote_branches, is_fast_forward};
 use crate::cli_util::{CommandHelper, RevisionArg};
 use crate::command_error::{user_error_with_hint, CommandError};
 use crate::ui::Ui;
@@ -50,7 +50,9 @@ pub fn cmd_branch_set(
     let mut new_branch_names: Vec<&str> = Vec::new();
     for name in branch_names {
         let old_target = repo.view().get_local_branch(name);
-        if old_target.is_absent() {
+        // If a branch is absent locally but is still tracking remote branches,
+        // we are resurrecting the local branch, not "creating" a new branch.
+        if old_target.is_absent() && !has_tracked_remote_branches(repo.view(), name) {
             new_branch_names.push(name);
         }
         if !args.allow_backwards && !is_fast_forward(repo, old_target, target_commit.id()) {

cli/tests/test_branch_command.rs

@@ -103,6 +103,14 @@ fn test_branch_move() {
     test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
     let repo_path = test_env.env_root().join("repo");
 
+    // Set up remote
+    let git_repo_path = test_env.env_root().join("git-repo");
+    git2::Repository::init_bare(git_repo_path).unwrap();
+    test_env.jj_cmd_ok(
+        &repo_path,
+        &["git", "remote", "add", "origin", "../git-repo"],
+    );
+
     let stderr = test_env.jj_cmd_failure(&repo_path, &["branch", "move", "foo"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: No such branch: foo
@@ -150,6 +158,40 @@ fn test_branch_move() {
         &["branch", "move", "--to=@-", "--allow-backwards", "foo"],
     );
     insta::assert_snapshot!(stderr, @"");
+
+    // Delete branch locally, but is still tracking remote
+    test_env.jj_cmd_ok(&repo_path, &["describe", "@-", "-mcommit"]);
+    test_env.jj_cmd_ok(&repo_path, &["git", "push", "-r@-"]);
+    test_env.jj_cmd_ok(&repo_path, &["branch", "delete", "foo"]);
+    insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
+    foo (deleted)
+      @origin: qpvuntsm 29a62310 (empty) commit
+    "###);
+
+    // Deleted tracking branch name should still be allocated
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["branch", "create", "foo"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Error: Tracked remote branches exist for deleted branch: foo
+    Hint: Use `jj branch set` to recreate the local branch. Run `jj branch untrack 'glob:foo@*'` to disassociate them.
+    "###);
+
+    // Restoring local target shouldn't invalidate tracking state
+    let (_stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["branch", "set", "foo"]);
+    insta::assert_snapshot!(stderr, @"");
+    insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
+    foo: mzvwutvl d5f17aba (empty) (no description set)
+      @origin (behind by 1 commits): qpvuntsm 29a62310 (empty) commit
+    "###);
+
+    // Untracked remote branch shouldn't block creation of local branch
+    test_env.jj_cmd_ok(&repo_path, &["branch", "untrack", "foo@origin"]);
+    test_env.jj_cmd_ok(&repo_path, &["branch", "delete", "foo"]);
+    let (_stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["branch", "create", "foo"]);
+    insta::assert_snapshot!(stderr, @"");
+    insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
+    foo: mzvwutvl d5f17aba (empty) (no description set)
+    foo@origin: qpvuntsm 29a62310 (empty) commit
+    "###);
 }
 
 #[test]
@@ -354,8 +396,14 @@ fn test_branch_rename() {
     let (_stdout, stderr) =
         test_env.jj_cmd_ok(&repo_path, &["branch", "rename", "bremote", "bremote2"]);
     insta::assert_snapshot!(stderr, @r###"
-    Warning: Branch bremote has tracking remote branches which were not renamed.
-    Hint: to rename the branch on the remote, you can `jj git push --branch bremote` first (to delete it on the remote), and then `jj git push --branch bremote2`. `jj git push --all` would also be sufficient.
+    Warning: Tracked remote branches for branch bremote were not renamed.
+    Hint: To rename the branch on the remote, you can `jj git push --branch bremote` first (to delete it on the remote), and then `jj git push --branch bremote2`. `jj git push --all` would also be sufficient.
+    "###);
+    let (_stdout, stderr) =
+        test_env.jj_cmd_ok(&repo_path, &["branch", "rename", "bremote2", "bremote"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Warning: Tracked remote branches for branch bremote exist.
+    Hint: Run `jj branch untrack 'glob:bremote@*'` to disassociate them.
     "###);
 }