Also use the unassigned stack names in the UI

Author: Byron

apps/desktop/cypress/e2e/support/mock/backend.ts

@@ -623,6 +623,7 @@ export default class MockBackend {
 
 		// Do nothing for now
 		return {
+			unappliedStacksShortNames: [],
 			stackId: 'something',
 			unappliedStacks: []
 		};

apps/desktop/src/lib/stacks/stack.ts

@@ -7,14 +7,43 @@ import type iconsJson from '@gitbutler/ui/data/icons.json';
 export type CreateBranchFromBranchOutcome = {
 	stackId: string;
 	unappliedStacks: string[];
+	unappliedStacksShortNames: string[];
 };
 
+function stackCount(numStacks: number): string {
+	if (numStacks === 1) {
+		return 'one stack';
+	} else {
+		return 'some stacks';
+	}
+}
+
+function prettyNamedListIfPossible(expectedNames: number, names: string[]): string {
+	// It could happen that not all stacks had names, for now we don't deal with that.
+	// Also, the old codepath doesn't produce names.
+	if (expectedNames !== names.length) {
+		return stackCount(expectedNames);
+	}
+	if (names.length === 0) {
+		return '';
+	} else if (names.length === 1) {
+		return `stack ${names[0]}`;
+	} else if (names.length === 2) {
+		return `stack ${names[0]} and stack ${names[1]}`;
+	}
+
+	const allButLast = names.slice(0, -1);
+	const last = names[names.length - 1];
+
+	return `${allButLast.map((n) => `stack ${n}`).join(', ')}, and stack ${last}`;
+}
+
 export function handleCreateBranchFromBranchOutcome(outcome: CreateBranchFromBranchOutcome) {
 	if (outcome.unappliedStacks.length > 0) {
 		showToast({
 			testId: TestId.StacksUnappliedToast,
-			title: 'Heads up: We had to unapply some stacks to apply this one',
-			message: `There were some conflicts detected when applying this branch into your workspace, so we automatically unapplied ${outcome.unappliedStacks.length} ${outcome.unappliedStacks.length === 1 ? 'stack' : 'stacks'}.
+			title: `Heads up: We had to unapply ${stackCount(outcome.unappliedStacks.length)} to apply this one`,
+			message: `There were some conflicts detected when applying this branch into your workspace, so we automatically unapplied ${prettyNamedListIfPossible(outcome.unappliedStacks.length, outcome.unappliedStacksShortNames)}.
 You can always re-apply them later from the branches page.`
 		});
 	}

crates/gitbutler-branch-actions/src/branch_manager/branch_creation.rs

@@ -192,15 +192,20 @@ impl BranchManager<'_> {
                 .id
                 .context("BUG: newly applied stacks should always have a stack id")?;
             let conflicted_stack_short_names_for_display = ws
-                .stacks
-                .iter()
-                .filter_map(|s| {
-                    out.conflicting_stack_ids
-                        .contains(&s.id?)
-                        .then(|| s.ref_name().map(|rn| rn.shorten().to_string()))
-                        .flatten()
+                .metadata
+                .as_ref()
+                .map(|md| {
+                    md.stacks
+                        .iter()
+                        .filter_map(|s| {
+                            out.conflicting_stack_ids
+                                .contains(&s.id)
+                                .then(|| s.ref_name().map(|rn| rn.shorten().to_string()))
+                                .flatten()
+                        })
+                        .collect::<Vec<_>>()
                 })
-                .collect();
+                .unwrap_or_default();
             return Ok((
                 applied_branch_stack_id,
                 out.conflicting_stack_ids,