fix: update error hints to reference subdir after path→subdir rename

internal/fetcher/fetcher.go

@@ -47,8 +47,8 @@ func Fetch(ctx context.Context, cacheRoot, name, repo, commit, version, path, ds
 
 		if !ok {
 			return time.Time{}, clierr.New(clierr.CodeConfig,
-				fmt.Sprintf("path %q of dependency %q not found at commit %.12s", path, name, commit),
-				"an empty or missing path is almost always a mistyped `path` — check the manifest",
+				fmt.Sprintf("subdir %q of dependency %q not found at commit %.12s", path, name, commit),
+				"an empty or missing subdir is almost always a typo — check the manifest",
 			)
 		}
 	}
@@ -74,8 +74,8 @@ func Fetch(ctx context.Context, cacheRoot, name, repo, commit, version, path, ds
 
 		if info, err := os.Stat(treeRoot); err != nil || !info.IsDir() {
 			return time.Time{}, clierr.New(clierr.CodeConfig,
-				fmt.Sprintf("path %q of dependency %q not found at commit %.12s", path, name, commit),
-				"an empty or missing path is almost always a mistyped `path` — check the manifest",
+				fmt.Sprintf("subdir %q of dependency %q is not a directory at commit %.12s", path, name, commit),
+				"a subdir must point at a directory in the dependency repo — check the manifest",
 			)
 		}
 	}

internal/fetcher/fetcher_test.go

@@ -171,6 +171,21 @@ func TestFetch_missingPath(t *testing.T) {
 	}
 }
 
+func TestFetch_pathIsFile(t *testing.T) {
+	t.Parallel()
+
+	r := gittest.New(t)
+	r.WriteFile("a.txt", "x\n")
+	sha := r.Commit("first")
+
+	// ls-tree reports the blob, so the pre-checkout existence check passes and
+	// the "not a directory" branch after checkout must catch it.
+	_, err := fetcher.Fetch(t.Context(), cacheRoot(t), depName, r.URL(), sha, "", "a.txt", fetchDst(t))
+	if got := clierr.ExitCode(err); got != int(clierr.CodeConfig) {
+		t.Fatalf("exit code = %d, want %d (error: %v)", got, clierr.CodeConfig, err)
+	}
+}
+
 func TestFetch_commitGone(t *testing.T) {
 	t.Parallel()
 

internal/hasher/hasher.go

@@ -165,7 +165,7 @@ func HashTree(root string) (string, error) {
 	if len(digests) == 0 {
 		return "", clierr.New(clierr.CodeConfig,
 			"the dependency tree contains no files",
-			"an empty dependency is almost always a mistyped `path` — check the manifest",
+			"an empty dependency is almost always a mistyped `subdir` — check the manifest",
 		)
 	}