split-index: don't compare cached data of entries already marked for split index

[thirdparty/git.git] / split-index.c

diff --git a/split-index.c b/split-index.c
index 548272ec338e8e9c5ca6aa75b6e4f0395f60aadc..187b910f5b5b83ae5fb236c58559157c8c195bf7 100644 (file)
--- a/split-index.c
+++ b/split-index.c
@@ -188,6 +188,30 @@ void merge_base_index(struct index_state *istate)
        si->saved_cache_nr = 0;
 }
 
+/*
+ * Compare most of the fields in two cache entries, i.e. all except the
+ * hashmap_entry and the name.
+ */
+static int compare_ce_content(struct cache_entry *a, struct cache_entry *b)
+{
+       const unsigned int ondisk_flags = CE_STAGEMASK | CE_VALID |
+                                         CE_EXTENDED_FLAGS;
+       unsigned int ce_flags = a->ce_flags;
+       unsigned int base_flags = b->ce_flags;
+       int ret;
+
+       /* only on-disk flags matter */
+       a->ce_flags &= ondisk_flags;
+       b->ce_flags &= ondisk_flags;
+       ret = memcmp(&a->ce_stat_data, &b->ce_stat_data,
+                    offsetof(struct cache_entry, name) -
+                    offsetof(struct cache_entry, ce_stat_data));
+       a->ce_flags = ce_flags;
+       b->ce_flags = base_flags;
+
+       return ret;
+}
+
 void prepare_to_write_split_index(struct index_state *istate)
 {
        struct split_index *si = init_split_index(istate);
@@ -207,13 +231,28 @@ void prepare_to_write_split_index(struct index_state *istate)
                 */
                for (i = 0; i < istate->cache_nr; i++) {
                        struct cache_entry *base;
-                       /* namelen is checked separately */
-                       const unsigned int ondisk_flags =
-                               CE_STAGEMASK | CE_VALID | CE_EXTENDED_FLAGS;
-                       unsigned int ce_flags, base_flags, ret;
                        ce = istate->cache[i];
-                       if (!ce->index)
+                       if (!ce->index) {
+                               /*
+                                * During simple update index operations this
+                                * is a cache entry that is not present in
+                                * the shared index.  It will be added to the
+                                * split index.
+                                *
+                                * However, it might also represent a file
+                                * that already has a cache entry in the
+                                * shared index, but a new index has just
+                                * been constructed by unpack_trees(), and
+                                * this entry now refers to different content
+                                * than what was recorded in the original
+                                * index, e.g. during 'read-tree -m HEAD^' or
+                                * 'checkout HEAD^'.  In this case the
+                                * original entry in the shared index will be
+                                * marked as deleted, and this entry will be
+                                * added to the split index.
+                                */
                                continue;
+                       }
                        if (ce->index > si->base->cache_nr) {
                                ce->index = 0;
                                continue;
@@ -227,18 +266,34 @@ void prepare_to_write_split_index(struct index_state *istate)
                                ce->index = 0;
                                continue;
                        }
-                       ce_flags = ce->ce_flags;
-                       base_flags = base->ce_flags;
-                       /* only on-disk flags matter */
-                       ce->ce_flags   &= ondisk_flags;
-                       base->ce_flags &= ondisk_flags;
-                       ret = memcmp(&ce->ce_stat_data, &base->ce_stat_data,
-                                    offsetof(struct cache_entry, name) -
-                                    offsetof(struct cache_entry, ce_stat_data));
-                       ce->ce_flags = ce_flags;
-                       base->ce_flags = base_flags;
-                       if (ret)
-                               ce->ce_flags |= CE_UPDATE_IN_BASE;
+                       /*
+                        * This is the copy of a cache entry that is present
+                        * in the shared index, created by unpack_trees()
+                        * while it constructed a new index.
+                        */
+                       if (ce->ce_flags & CE_UPDATE_IN_BASE) {
+                               /*
+                                * Already marked for inclusion in the split
+                                * index, either because the corresponding
+                                * file was modified and the cached stat data
+                                * was refreshed, or because the original
+                                * entry already had a replacement entry in
+                                * the split index.
+                                * Nothing to do.
+                                */
+                       } else {
+                               /*
+                                * Thoroughly compare the cached data to see
+                                * whether it should be marked for inclusion
+                                * in the split index.
+                                *
+                                * This comparison might be unnecessary, as
+                                * code paths modifying the cached data do
+                                * set CE_UPDATE_IN_BASE as well.
+                                */
+                               if (compare_ce_content(ce, base))
+                                       ce->ce_flags |= CE_UPDATE_IN_BASE;
+                       }
                        discard_cache_entry(base);
                        si->base->cache[ce->index - 1] = ce;
                }