+ }
+ if (old)
+ reject_merge(old);
+}
+
+/*
+ * When we find a "stage2" entry in the two-way merge, that's
+ * the one that will remain. If we have an exact old match,
+ * we don't care whether the file is up-to-date or not, we just
+ * re-use the thing directly.
+ *
+ * If we didn't have an exact match, then we want to make sure
+ * that we've seen a stage1 that matched the old, and that the
+ * old file was up-to-date. Because it will be gone after this
+ * merge..
+ */
+static void twoway_check(struct cache_entry *old, int seen_stage1, struct cache_entry *ce)
+{
+ if (path_matches(old, ce)) {
+ /*
+ * This also removes the UPDATE flag on
+ * a match
+ */
+ if (same(old, ce)) {
+ *ce = *old;
+ return;
+ }
+ if (!seen_stage1)
+ reject_merge(old);
+ }
+ verify_uptodate(old);
+}
+
+/*
+ * Two-way merge.
+ *
+ * The rule is:
+ * - every current entry has to match the old tree
+ * - if the current entry matches the new tree, we leave it
+ * as-is. Otherwise we require that it be up-to-date.
+ */
+static void twoway_merge(struct cache_entry **src, int nr)
+{
+ int seen_stage1 = 0;
+ struct cache_entry *old = NULL;
+ struct cache_entry **dst = src;
+
+ while (nr--) {
+ struct cache_entry *ce = *src++;
+ int stage = ce_stage(ce);
+
+ switch (stage) {
+ case 0:
+ if (old)
+ reject_merge(old);
+ old = ce;
+ seen_stage1 = 0;
+ active_nr--;
+ continue;
+
+ case 1:
+ active_nr--;
+ if (!old)
+ continue;
+ if (!path_matches(old, ce) || !same(old, ce))
+ reject_merge(old);
+ seen_stage1 = 1;
+ continue;
+
+ case 2:
+ ce->ce_flags |= htons(CE_UPDATE);
+ if (old) {
+ twoway_check(old, seen_stage1, ce);
+ old = NULL;
+ }
+ ce->ce_flags &= ~htons(CE_STAGEMASK);
+ *dst++ = ce;
+ continue;
+ }
+ die("impossible two-way stage");
+ }
+
+ /*
+ * Unmatched with a new entry? Make sure it was
+ * at least uptodate in the working directory _and_
+ * the original tree..
+ */
+ if (old) {
+ if (!seen_stage1)
+ reject_merge(old);
+ verify_uptodate(old);