[PATCH] read-tree: loosen too strict index requirements

This patch teaches read-tree 3-way merge that, when only "the
other tree" changed a path, and if the index file already has
the same change, we are not in a situation that would clobber
the index and the work tree, and lets the merge succeed; this is
case #14ALT in t1000 test.  It does not change the result of the
merge, but prevents it from failing when it does not have to.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/read-tree.c b/read-tree.c
index d86cc02..0d94fe2 100644 (file)
--- a/read-tree.c
+++ b/read-tree.c
@@ -280,6 +280,12 @@ static int threeway_merge(struct cache_entry *stages[4],
                }
                /* otherwise we will apply the original rule */
        }
+       /* #14ALT */
+       if (a && b && c && same(a, b) && !same(a, c)) {
+               if (old && same(old, c))
+                       return merged_entry_allow_dirty(c, old, dst);
+               /* otherwise the regular rule applies */
+       }
        /*
         * If we have an entry in the index cache ("old"), then we want
         * to make sure that it matches any entries in stage 2 ("first

diff --git a/t/t1000-read-tree-m-3way.sh b/t/t1000-read-tree-m-3way.sh
index 3d9b3ac..89f0e81 100755 (executable)
--- a/t/t1000-read-tree-m-3way.sh
+++ b/t/t1000-read-tree-m-3way.sh
@@ -464,6 +464,15 @@ test_expect_success \
      git-read-tree -m $tree_O $tree_A $tree_B &&
      check_result"
 
+test_expect_success \
+    '14 - may match B in O && A && B && O==A && O!=B case' \
+    "rm -f .git/index NM &&
+     cp .orig-B/NM NM &&
+     git-update-cache --add NM &&
+     echo extra >>NM &&
+     git-read-tree -m $tree_O $tree_A $tree_B &&
+     check_result"
+
 test_expect_failure \
     '14 (fail) - must match and be up-to-date in O && A && B && O==A && O!=B case' \
     "rm -f .git/index NM &&