Auto-stage resolved conflicts when switching branches

Fixes #86

Author: pol-rivero

app/src/lib/git/stage.ts

@@ -61,3 +61,37 @@ export async function stageManualConflictResolution(
       assertNever(chosen, 'unaccounted for git status entry possibility')
   }
 }
+
+/**
+ * Stages all resolved conflict files before a checkout operation to prevent
+ * "error: you need to resolve your current index first" from git.
+ *
+ * Handles two kinds of resolved conflicts:
+ *  - Text conflicts resolved in an external editor (conflictMarkerCount === 0)
+ *  - Manual conflicts where the user chose ours/theirs in the Desktop UI
+ */
+export async function stageResolvedConflictFiles(
+  repository: Repository,
+  files: ReadonlyArray<WorkingDirectoryFileChange>,
+  manualResolutions: ReadonlyMap<string, ManualConflictResolution>
+): Promise<void> {
+  for (const file of files) {
+    const { status } = file
+    if (!isConflictedFileStatus(status)) {
+      continue
+    }
+
+    const manualResolution = manualResolutions.get(file.path)
+
+    if (manualResolution !== undefined) {
+      // Binary/manual conflict resolved via Desktop UI — stage it
+      await stageManualConflictResolution(repository, file, manualResolution)
+    } else if (
+      isConflictWithMarkers(status) &&
+      status.conflictMarkerCount === 0
+    ) {
+      // Text conflict resolved in external editor — stage it
+      await addConflictedFile(repository, file)
+    }
+  }
+}

app/src/lib/stores/app-store.ts

@@ -286,6 +286,7 @@ import {
 import { determineMergeability } from '../git/merge-tree'
 import { reorder } from '../git/reorder'
 import { squash } from '../git/squash'
+import { stageResolvedConflictFiles } from '../git/stage'
 import {
   createDesktopStashEntry,
   dropDesktopStashEntry,
@@ -4428,6 +4429,14 @@ export class AppStore extends TypedBaseStore<IAppState> {
       }
     }
 
+    // Auto-stage resolved conflict files before checkout to prevent
+    // "error: you need to resolve your current index first"
+    await stageResolvedConflictFiles(
+      repository,
+      changesState.workingDirectory.files,
+      changesState.conflictState?.manualResolutions ?? new Map()
+    )
+
     return this.withRefreshedGitHubRepository(repository, repository => {
       // We always want to end with refreshing the repository regardless of
       // whether the checkout succeeded or not in order to present the most