update-index/diff-index: use core.preloadindex to improve performance

diff --git a/builtin/diff.c b/builtin/diff.c
index 9650be2c50e6f79dbe033fae39f490d49c6318da..198b9216a47e646e1372085e103cf8e72da31eba 100644 (file)
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -130,8 +130,6 @@ static int builtin_diff_index(struct rev_info *revs,
                        usage(builtin_diff_usage);
                argv++; argc--;
        }
-       if (!cached)
-               setup_work_tree();
        /*
         * Make sure there is one revision (i.e. pending object),
         * and there is no revision filtering parameters.
@@ -140,8 +138,14 @@ static int builtin_diff_index(struct rev_info *revs,
            revs->max_count != -1 || revs->min_age != -1 ||
            revs->max_age != -1)
                usage(builtin_diff_usage);
-       if (read_cache_preload(revs->diffopt.pathspec.raw) < 0) {
-               perror("read_cache_preload");
+       if (!cached) {
+               setup_work_tree();
+               if (read_cache_preload(revs->diffopt.pathspec.raw) < 0) {
+                       perror("read_cache_preload");
+                       return -1;
+               }
+       } else if (read_cache() < 0) {
+               perror("read_cache");
                return -1;
        }
        return run_diff_index(revs, cached);