submodule loading: separate code path for .gitmodules and config overlay

diff --git a/unpack-trees.c b/unpack-trees.c
index 6b7356dab2a100f2c402af59c4207bfc291cd59d..d98a4f4d8668d989d34e5b938947704836ae8c84 100644 (file)
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -252,14 +252,18 @@ static int check_submodule_move_head(const struct cache_entry *ce,
                                     const char *new_id,
                                     struct unpack_trees_options *o)
 {
+       unsigned flags = SUBMODULE_MOVE_HEAD_DRY_RUN;
        const struct submodule *sub = submodule_from_ce(ce);
        if (!sub)
                return 0;
 
+       if (o->reset)
+               flags |= SUBMODULE_MOVE_HEAD_FORCE;
+
        switch (sub->update_strategy.type) {
        case SM_UPDATE_UNSPECIFIED:
        case SM_UPDATE_CHECKOUT:
-               if (submodule_move_head(ce->name, old_id, new_id, SUBMODULE_MOVE_HEAD_DRY_RUN))
+               if (submodule_move_head(ce->name, old_id, new_id, flags))
                        return o->gently ? -1 :
                                add_rejected_path(o, ERROR_WOULD_LOSE_SUBMODULE, ce->name);
                return 0;
@@ -308,6 +312,7 @@ static void unlink_entry(const struct cache_entry *ce)
                case SM_UPDATE_CHECKOUT:
                case SM_UPDATE_REBASE:
                case SM_UPDATE_MERGE:
+                       /* state.force is set at the caller. */
                        submodule_move_head(ce->name, "HEAD", NULL,
                                            SUBMODULE_MOVE_HEAD_FORCE);
                        break;
@@ -604,12 +609,18 @@ static int switch_cache_bottom(struct traverse_info *info)
        return ret;
 }
 
+static inline int are_same_oid(struct name_entry *name_j, struct name_entry *name_k)
+{
+       return name_j->oid && name_k->oid && !oidcmp(name_j->oid, name_k->oid);
+}
+
 static int traverse_trees_recursive(int n, unsigned long dirmask,
                                    unsigned long df_conflicts,
                                    struct name_entry *names,
                                    struct traverse_info *info)
 {
        int i, ret, bottom;
+       int nr_buf = 0;
        struct tree_desc t[MAX_UNPACK_TREES];
        void *buf[MAX_UNPACK_TREES];
        struct traverse_info newinfo;
@@ -626,18 +637,40 @@ static int traverse_trees_recursive(int n, unsigned long dirmask,
        newinfo.pathlen += tree_entry_len(p) + 1;
        newinfo.df_conflicts |= df_conflicts;
 
+       /*
+        * Fetch the tree from the ODB for each peer directory in the
+        * n commits.
+        *
+        * For 2- and 3-way traversals, we try to avoid hitting the
+        * ODB twice for the same OID.  This should yield a nice speed
+        * up in checkouts and merges when the commits are similar.
+        *
+        * We don't bother doing the full O(n^2) search for larger n,
+        * because wider traversals don't happen that often and we
+        * avoid the search setup.
+        *
+        * When 2 peer OIDs are the same, we just copy the tree
+        * descriptor data.  This implicitly borrows the buffer
+        * data from the earlier cell.
+        */
        for (i = 0; i < n; i++, dirmask >>= 1) {
-               const unsigned char *sha1 = NULL;
-               if (dirmask & 1)
-                       sha1 = names[i].oid->hash;
-               buf[i] = fill_tree_descriptor(t+i, sha1);
+               if (i > 0 && are_same_oid(&names[i], &names[i - 1]))
+                       t[i] = t[i - 1];
+               else if (i > 1 && are_same_oid(&names[i], &names[i - 2]))
+                       t[i] = t[i - 2];
+               else {
+                       const unsigned char *sha1 = NULL;
+                       if (dirmask & 1)
+                               sha1 = names[i].oid->hash;
+                       buf[nr_buf++] = fill_tree_descriptor(t+i, sha1);
+               }
        }
 
        bottom = switch_cache_bottom(&newinfo);
        ret = traverse_trees(n, t, &newinfo);
        restore_cache_bottom(&newinfo, bottom);
 
-       for (i = 0; i < n; i++)
+       for (i = 0; i < nr_buf; i++)
                free(buf[i]);
 
        return ret;