Assure that an entrypoint doesn't alter the stack setup.

I.e. if stacks are separate when looking at the workspace, they
should remain separtate when one of these is checked out directly.

Author: Byron

crates/but-graph/tests/fixtures/scenarios.sh

@@ -298,6 +298,14 @@ mkdir ws
      create_workspace_commit_once main
   )
 
+  git init just-init-with-two-branches
+  (cd just-init-with-two-branches
+    commit init
+    git branch A
+    git branch B
+    git checkout -b gitbutler/workspace
+  )
+
   git init just-init-with-branches
   (cd just-init-with-branches
     commit init && setup_target_to_match_main

crates/but-graph/tests/graph/init/with_workspace.rs

@@ -681,6 +681,58 @@ fn minimal_merge() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[test]
+fn stack_configuration_is_respected_if_one_of_them_is_an_entrypoint() -> anyhow::Result<()> {
+    let (repo, mut meta) = read_only_in_memory_scenario("ws/just-init-with-two-branches")?;
+    insta::assert_snapshot!(visualize_commit_graph_all(&repo)?, @"* fafd9d0 (HEAD -> gitbutler/workspace, main, B, A) init");
+
+    add_stack_with_segments(&mut meta, 1, "A", StackState::InWorkspace, &[]);
+    add_stack_with_segments(&mut meta, 2, "B", StackState::InWorkspace, &[]);
+
+    let graph = Graph::from_head(
+        &repo,
+        &*meta,
+        standard_options_with_extra_target(&repo, "main"),
+    )?
+    .validated()?;
+    insta::assert_snapshot!(graph_tree(&graph), @r"
+    └── 👉📕►►►:0[0]:gitbutler/workspace
+        ├── 📙►:2[1]:A
+        │   └── ►:1[2]:anon:
+        │       └── ·fafd9d0 (⌂|🏘️|1) ►main
+        └── 📙►:3[1]:B
+            └── →:1:
+    ");
+    insta::assert_snapshot!(graph_workspace(&graph.to_workspace()?), @r"
+    📕🏘️⚠️:0:gitbutler/workspace <> ✓! on fafd9d0
+    ├── ≡📙:3:B on fafd9d0
+    │   └── 📙:3:B
+    └── ≡📙:2:A on fafd9d0
+        └── 📙:2:A
+    ");
+
+    let (id, ref_name) = id_at(&repo, "B");
+    let graph = Graph::from_commit_traversal(id, ref_name.clone(), &*meta, standard_options())?
+        .validated()?;
+    // TODO: it shouldn't create a dependent branch here, but instead see A as a stack.
+    //       problem is that for stack creation, there is no candidate.
+    insta::assert_snapshot!(graph_tree(&graph), @r"
+    └── 📕►►►:1[0]:gitbutler/workspace
+        └── 👉📙►:0[1]:B
+            └── 📙►:2[2]:A
+                └── ·fafd9d0 (⌂|🏘️|1) ►main
+    ");
+    insta::assert_snapshot!(graph_workspace(&graph.to_workspace()?), @r"
+    📕🏘️⚠️:1:gitbutler/workspace <> ✓!
+    └── ≡👉📙:0:B
+        ├── 👉📙:0:B
+        └── 📙:2:A
+            └── ·fafd9d0 (🏘️) ►main
+    ");
+
+    Ok(())
+}
+
 #[test]
 fn just_init_with_branches() -> anyhow::Result<()> {
     let (repo, mut meta) = read_only_in_memory_scenario("ws/just-init-with-branches")?;