[PATCH/RFC 2/2] merge-recursive: Handle rename/rename/delete/delete conflicts.

[Nicolas Cavallari]

On a rename 2to1 conflict, where both a and b are renamed to c,
the other branch may have deleted a or b.  This currently luckily
works for files but fails for symlinks.

Fix conflict_rename_rename_2to1 to not merge_file_special_markers()
with diff_filespecs where mode == 0.  The alternative would be to make
merge_file_1() handle it.

Mark the corresponding testcase in t6042 as fixed.

Signed-off-by: Nicolas Cavallari <nicolas.cavall...@green-communications.fr>
---
 merge-recursive.c                    | 28 ++++++++++++++++++++++------
 t/t6042-merge-rename-corner-cases.sh |  2 +-
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index b7ff1ada3..0e5a3e3ed 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1305,13 +1305,29 @@ static int conflict_rename_rename_2to1(struct 
merge_options *o,
        remove_file(o, 1, a->path, o->call_depth || 
would_lose_untracked(a->path));
        remove_file(o, 1, b->path, o->call_depth || 
would_lose_untracked(b->path));
 
-       if (merge_file_special_markers(o, a, c1, &ci->ren1_other,
-                                      o->branch1, c1->path,
-                                      o->branch2, ci->ren1_other.path, 
&mfi_c1) ||
-           merge_file_special_markers(o, b, &ci->ren2_other, c2,
-                                      o->branch1, ci->ren2_other.path,
-                                      o->branch2, c2->path, &mfi_c2))
+       // The other branch may have deleted a, as indicated by mode == 0.
+       if (ci->ren1_other.mode == 0) {
+               mfi_c1.clean = 0;
+               mfi_c1.merge = 0;
+               mfi_c1.mode = c1->mode;
+               oidcpy(&mfi_c1.oid, &c1->oid);
+       } else if (merge_file_special_markers(o, a, c1, &ci->ren1_other,
+                                             o->branch1, c1->path,
+                                             o->branch2, ci->ren1_other.path,
+                                             &mfi_c1)) {
                return -1;
+       }
+
+       if (ci->ren2_other.mode == 0) {
+               mfi_c2.clean = 0;
+               mfi_c2.merge = 0;
+               mfi_c2.mode = c2->mode;
+               oidcpy(&mfi_c2.oid, &c2->oid);
+       } else if (merge_file_special_markers(o, b, &ci->ren2_other, c2,
+                                             o->branch1, ci->ren2_other.path,
+                                             o->branch2, c2->path, &mfi_c2)) {
+               return -1;
+       }
 
        if (o->call_depth) {
                /*
diff --git a/t/t6042-merge-rename-corner-cases.sh 
b/t/t6042-merge-rename-corner-cases.sh
index ea4e14cbd..34b16d5d7 100755
--- a/t/t6042-merge-rename-corner-cases.sh
+++ b/t/t6042-merge-rename-corner-cases.sh
@@ -605,7 +605,7 @@ test_expect_success 'setup rename/rename/delete/delete 
conflict' '
        git commit -m C
 '
 
-test_expect_failure 'rename/rename/delete/delete leaves at least one file' '
+test_expect_success 'rename/rename/delete/delete leaves at least one file' '
        git checkout B^0 &&
        test_must_fail git merge -s recursive C^0 &&
 
-- 
2.11.0