fix(delete): fetch each repo once across all candidate workspaces

Collecting worktree paths from N workspaces produced N distinct entries
for the same underlying repo, bypassing Set deduplication and causing
redundant fetches. Now deduplicates by repo name and fetches from
canonical repo dirs in .arb/repos/, matching the pattern used by all
other multi-repo fetch paths.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: henrikje

src/commands/delete.ts

@@ -338,20 +338,21 @@ export function registerDeleteCommand(program: Command, getCtx: () => ArbContext
         // Pre-fetch repos across all candidate workspaces for fresh remote data
         const fetchWorkspaceRepos = async (workspaceNames: string[]) => {
           if (options.fetch === false) return;
-          const allRepoDirs = new Set<string>();
           const allRepoNames = new Set<string>();
           for (const ws of workspaceNames) {
             const wsDir = `${ctx.arbRootDir}/${ws}`;
             for (const repoDir of workspaceRepoDirs(wsDir)) {
-              allRepoDirs.add(repoDir);
               allRepoNames.add(basename(repoDir));
             }
           }
-          if (allRepoDirs.size === 0) return;
+          if (allRepoNames.size === 0) return;
+          // Fetch from canonical repo dirs so each repo is only fetched once,
+          // regardless of how many workspaces reference it.
+          const allRepoDirs = [...allRepoNames].map((name) => `${ctx.reposDir}/${name}`);
           const cache = new GitCache();
           await assertMinimumGitVersion(cache);
           const remotesMap = await cache.resolveRemotesMap([...allRepoNames], ctx.reposDir);
-          const fetchResults = await parallelFetch([...allRepoDirs], undefined, remotesMap);
+          const fetchResults = await parallelFetch(allRepoDirs, undefined, remotesMap);
           reportFetchFailures([...allRepoNames], fetchResults);
         };
 

test/integration/workspace-membership.test.ts

@@ -947,4 +947,20 @@ describe("delete empty workspace", () => {
       expect(result.exitCode).toBe(0);
       expect(existsSync(join(env.projectDir, "my-feature"))).toBe(false);
     }));
+
+  test("arb delete --all-safe fetches each repo only once across multiple workspaces", () =>
+    withEnv(async (env) => {
+      // Create multiple workspaces all using the same single repo
+      await arb(env, ["create", "ws-one", "repo-a"]);
+      await arb(env, ["create", "ws-two", "repo-a"]);
+      await arb(env, ["create", "ws-three", "repo-a"]);
+      await git(join(env.projectDir, "ws-one/repo-a"), ["push", "-u", "origin", "ws-one"]);
+      await git(join(env.projectDir, "ws-two/repo-a"), ["push", "-u", "origin", "ws-two"]);
+      await git(join(env.projectDir, "ws-three/repo-a"), ["push", "-u", "origin", "ws-three"]);
+
+      const result = await arb(env, ["delete", "--all-safe", "--yes", "--force"]);
+      expect(result.exitCode).toBe(0);
+      // Should report "1 repo" fetched, not "3 repos"
+      expect(result.output).toMatch(/Fetched 1 repo in/);
+    }));
 });