Fix "read-tree -m A B" priming the cache-tree

In 456156d a shortcut to priming the index tree reference was
introduced, but the justification for it was completely bogus.

"read-tree -m A B" is to take the index (and the working tree)
that is largely based on (but does not have to match exactly) A
and update it to B, while carrying the local change that does
not overlap the difference between A and B, so there is no reason
to expect that the resulting index should match the tree B.

Noticed and test provided by Heiko Voigt.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-read-tree.c b/builtin-read-tree.c
index 82e25eaa0758d8b9584592f4072f81eeccb0bf1d..4fbf5f82ae541ea31954ecfed0f908e471910549 100644 (file)
--- a/builtin-read-tree.c
+++ b/builtin-read-tree.c
@@ -199,14 +199,9 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
         * "-m ent" or "--reset ent" form), we can obtain a fully
         * valid cache-tree because the index must match exactly
         * what came from the tree.
-        *
-        * The same holds true if we are switching between two trees
-        * using read-tree -m A B.  The index must match B after that.
         */
        if (nr_trees == 1 && !opts.prefix)
                prime_cache_tree(&active_cache_tree, trees[0]);
-       else if (nr_trees == 2 && opts.merge)
-               prime_cache_tree(&active_cache_tree, trees[1]);
 
        if (write_cache(newfd, active_cache, active_nr) ||
            commit_locked_index(&lock_file))

diff --git a/t/t1001-read-tree-m-2way.sh b/t/t1001-read-tree-m-2way.sh
index 271bc4e17f0c12cda550ffa4f54f1ad7555b3bed..6e3b60110381bca4cbd235f73b5c5b837b57a512 100755 (executable)
--- a/t/t1001-read-tree-m-2way.sh
+++ b/t/t1001-read-tree-m-2way.sh
@@ -392,4 +392,20 @@ test_expect_success \
      git ls-files --stage | tee >treeMcheck.out &&
      test_cmp treeM.out treeMcheck.out'
 
+test_expect_success '-m references the correct modified tree' '
+       echo >file-a &&
+       echo >file-b &&
+       git add file-a file-b &&
+       git commit -a -m "test for correct modified tree"
+       git branch initial-mod &&
+       echo b >file-b &&
+       git commit -a -m "B" &&
+       echo a >file-a &&
+       git add file-a &&
+       git ls-tree $(git write-tree) file-a >expect &&
+       git read-tree -m HEAD initial-mod &&
+       git ls-tree $(git write-tree) file-a >actual &&
+       test_cmp expect actual
+'
+
 test_done