for-each-ref: Do not lookup objects when they will not be used

This makes commands such as `git for-each-ref --format='%(refname)'`,
which are used heavily by the bash_completion code, run about 6 times
faster on an uncached repository (3 s intead of 18 s on my linux-2.6
repository with several remotes).

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-for-each-ref.c b/builtin-for-each-ref.c
index d091e04af9549b70a1e15a4b845383056e71932e..1911cda1c29ef4cb6f0785226efcb1d3cb07ef3e 100644 (file)
--- a/builtin-for-each-ref.c
+++ b/builtin-for-each-ref.c
@@ -561,14 +561,6 @@ static void populate_value(struct refinfo *ref)
 
        ref->value = xcalloc(sizeof(struct atom_value), used_atom_cnt);
 
-       buf = get_obj(ref->objectname, &obj, &size, &eaten);
-       if (!buf)
-               die("missing object %s for %s",
-                   sha1_to_hex(ref->objectname), ref->refname);
-       if (!obj)
-               die("parse_object_buffer failed on %s for %s",
-                   sha1_to_hex(ref->objectname), ref->refname);
-
        /* Fill in specials first */
        for (i = 0; i < used_atom_cnt; i++) {
                const char *name = used_atom[i];
@@ -621,6 +613,22 @@ static void populate_value(struct refinfo *ref)
                }
        }
 
+       for (i = 0; i < used_atom_cnt; i++) {
+               struct atom_value *v = &ref->value[i];
+               if (v->s == NULL)
+                       goto need_obj;
+       }
+       return;
+
+ need_obj:
+       buf = get_obj(ref->objectname, &obj, &size, &eaten);
+       if (!buf)
+               die("missing object %s for %s",
+                   sha1_to_hex(ref->objectname), ref->refname);
+       if (!obj)
+               die("parse_object_buffer failed on %s for %s",
+                   sha1_to_hex(ref->objectname), ref->refname);
+
        grab_values(ref->value, 0, obj, buf, size);
        if (!eaten)
                free(buf);
@@ -926,7 +934,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 
        memset(&cbdata, 0, sizeof(cbdata));
        cbdata.grab_pattern = argv;
-       for_each_ref(grab_single_ref, &cbdata);
+       for_each_rawref(grab_single_ref, &cbdata);
        refs = cbdata.grab_array;
        num_refs = cbdata.grab_cnt;