Add support for creating dependent branches in workspaces

With and without workspace commits

Author: Byron

crates/but-workspace/src/branch.rs

@@ -611,6 +611,8 @@ mod create_reference {
 pub use create_reference::*;
 
 /// Create a new reference named `ref_name` to point at a commit relative to `anchor`.
+/// If `anchor` is `None` this means the branch should be placed above the lower bound of the workspace if this
+/// is unambiguous, i.e. if there is no stack, or a single stack.
 /// The resulting reference will be created in `repo` and `meta` will be updated for `ref_name` so the workspace
 /// contains it, but only if it's a managed workspace, along with branch metadata.
 ///
@@ -622,20 +624,24 @@ pub use create_reference::*;
 /// Return a regenerated Graph that contains the new reference, and from which a new workspace can be derived.
 pub fn create_reference_as_segment(
     ref_name: &gix::refs::FullNameRef,
-    anchor: ReferenceAnchor,
+    anchor: impl Into<Option<ReferenceAnchor>>,
     repo: &gix::Repository,
     workspace: &but_graph::projection::Workspace<'_>,
     meta: &mut impl RefMetadata,
 ) -> anyhow::Result<but_graph::Graph> {
+    let anchor = anchor.into();
     let commit_id = {
         match anchor {
-            ReferenceAnchor::AtCommit {
+            None => {
+                todo!("on top of singular stack/no stack")
+            }
+            Some(ReferenceAnchor::AtCommit {
                 commit_id,
                 position,
-            } => position.resolve_commit(
+            }) => position.resolve_commit(
                 workspace.lookup_commit(workspace.try_find_owner_indexes_by_commit_id(commit_id)?),
             )?,
-            ReferenceAnchor::AtSegment { ref_name, position } => {
+            Some(ReferenceAnchor::AtSegment { ref_name, position }) => {
                 // TODO: can this be unified?
                 if workspace.has_metadata() {
                     let (stack_idx, seg_idx) =

crates/but-workspace/tests/fixtures/generated-archives/.gitignore

@@ -31,3 +31,4 @@
 /with-remotes-and-workspace.tar
 /with-conflict.tar
 /journey*.tar
+/single-branch*.tar

crates/but-workspace/tests/fixtures/scenario/shared.sh

@@ -1,3 +1,7 @@
+
+# Just to save a line in the scripts that use this module
+set -eu -o pipefail
+
 function remote_tracking_caught_up() {
   setup_remote_tracking "$1"
 }

crates/but-workspace/tests/fixtures/scenario/single-branch-10-commits.sh

@@ -1,10 +1,10 @@
 #!/usr/bin/env bash
 
 ### Description
-# A single default branch with 10 commits in it.
 set -eu -o pipefail
 
 git init
+echo "A single default branch with 10 commits in it." >.git/description
 for count in $(seq 10); do
   echo $count >file && git add . && git commit -m $count
 done

crates/but-workspace/tests/fixtures/scenario/single-branch-no-ws-commit-no-target.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+### Description
+source "${BASH_SOURCE[0]%/*}/shared.sh"
+
+git init
+echo "Single commit, no main remote/target, no ws commit, but ws-reference" >.git/description
+
+commit M1
+git checkout -b gitbutler/workspace

crates/but-workspace/tests/fixtures/scenario/single-branch-no-ws-commit.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+### Description
+source "${BASH_SOURCE[0]%/*}/shared.sh"
+
+git init
+echo "Single commit, target, no ws commit, but ws-reference" >.git/description
+
+commit M1
+setup_target_to_match_main
+git checkout -b gitbutler/workspace

crates/but-workspace/tests/workspace/branch.rs

@@ -13,6 +13,7 @@ mod create_reference_as_segment {
     mod with_workspace {
         use crate::ref_info::with_workspace_commit::utils::{
             StackState, add_stack_with_segments, named_read_only_in_memory_scenario,
+            named_writable_scenario_with_description,
         };
         use crate::utils::r;
         use but_core::RefMetadata;
@@ -22,6 +23,58 @@ mod create_reference_as_segment {
         use but_workspace::branch::ReferenceAnchor;
         use but_workspace::branch::ReferencePosition::*;
 
+        #[test]
+        fn journey_no_ws_commit_no_target() -> anyhow::Result<()> {
+            let (_tmp, repo, meta, desc) =
+                named_writable_scenario_with_description("single-branch-no-ws-commit-no-target")?;
+            insta::assert_snapshot!(desc, @"Single commit, no main remote/target, no ws commit, but ws-reference");
+
+            insta::assert_snapshot!(visualize_commit_graph_all(&repo)?, @"* 3183e43 (HEAD -> gitbutler/workspace, main) M1");
+
+            let graph = but_graph::Graph::from_head(
+                &repo,
+                &meta,
+                Options {
+                    extra_target_commit_id: id_by_rev(&repo, "main").detach().into(),
+                    ..Options::limited()
+                },
+            )?;
+            let ws = graph.to_workspace()?;
+
+            // And even though setting an extra-target works like it should, i.e a simulated target
+            // which we can store in absence of a selected target branch…
+            insta::assert_snapshot!(graph_workspace(&ws), @"📕🏘️⚠️:0:gitbutler/workspace <> ✓! on 3183e43");
+
+            // …we chose to work with an open-ended workspace just to struggle more.
+            let graph = but_graph::Graph::from_head(&repo, &meta, Options::limited())?;
+            let ws = graph.to_workspace()?;
+            insta::assert_snapshot!(graph_workspace(&ws), @r"
+            📕🏘️⚠️:0:gitbutler/workspace <> ✓!
+            └── ≡:1:main
+                └── :1:main
+                    └── ·3183e43 (🏘️)
+            ");
+
+            Ok(())
+        }
+
+        #[test]
+        fn journey_no_ws_commit() -> anyhow::Result<()> {
+            let (_tmp, repo, meta, desc) =
+                named_writable_scenario_with_description("single-branch-no-ws-commit")?;
+            insta::assert_snapshot!(desc, @"Single commit, target, no ws commit, but ws-reference");
+
+            insta::assert_snapshot!(visualize_commit_graph_all(&repo)?, @"* 3183e43 (HEAD -> gitbutler/workspace, origin/main, main) M1");
+
+            let graph = but_graph::Graph::from_head(&repo, &meta, Options::limited())?;
+            let ws = graph.to_workspace()?;
+
+            insta::assert_snapshot!(graph_workspace(&ws), @"📕🏘️⚠️:0:gitbutler/workspace <> ✓refs/remotes/origin/main on 3183e43");
+            // TODO: more anchor tests.
+
+            Ok(())
+        }
+
         #[test]
         fn error1() -> anyhow::Result<()> {
             let (repo, mut meta) = named_read_only_in_memory_scenario(

crates/but-workspace/tests/workspace/ref_info/with_workspace_commit/mod.rs

@@ -3364,9 +3364,14 @@ pub(crate) mod utils {
         Ok((repo, meta))
     }
 
-    pub fn named_writable_scenario(
+    pub fn named_writable_scenario_with_description(
         name: &str,
-    ) -> anyhow::Result<(TempDir, gix::Repository, VirtualBranchesTomlMetadata)> {
+    ) -> anyhow::Result<(
+        TempDir,
+        gix::Repository,
+        VirtualBranchesTomlMetadata,
+        String,
+    )> {
         let (tmp, repo, mut meta) = crate::ref_info::utils::named_writable_scenario(name)?;
         let vb = meta.data_mut();
         vb.default_target = Some(Target {
@@ -3382,7 +3387,15 @@ pub(crate) mod utils {
                 .unwrap_or_else(|| gix::hash::Kind::Sha1.null()),
             push_remote_name: None,
         });
-        Ok((tmp, repo, meta))
+        let desc = std::fs::read_to_string(repo.git_dir().join("description"))?;
+        Ok((tmp, repo, meta, desc))
+    }
+
+    pub fn named_writable_scenario(
+        name: &str,
+    ) -> anyhow::Result<(TempDir, gix::Repository, VirtualBranchesTomlMetadata)> {
+        let (a, b, c, _desc) = named_writable_scenario_with_description(name)?;
+        Ok((a, b, c))
     }
 
     pub fn named_read_only_in_memory_scenario_with_description(