am --abort: revert changes introduced by failed 3way merge

Even when a merge conflict occurs with am --3way, the index will be
modified with the results of any successfully merged files. These
changes to the index will not be reverted with a
"git read-tree --reset -u HEAD ORIG_HEAD", as git read-tree will not be
aware of how the current index differs from HEAD or ORIG_HEAD.

To fix this, we first reset any conflicting entries in the index. The
resulting index will contain the results of successfully merged files
introduced by the failed merge. We write this index to a tree, and then
use git read-tree to fast-forward this "index tree" back to ORIG_HEAD,
thus undoing all the changes from the failed merge.

When we are on an unborn branch, HEAD and ORIG_HEAD will not point to
valid trees. In this case, use an empty tree.

Signed-off-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-am.sh b/git-am.sh
index e0d067c00e6a4405ea59ab51c5e1ce3fbaf80b0c..f71d7bb99716a096b8cc95dce8a05a0de1d2d8e7 100755 (executable)
--- a/git-am.sh
+++ b/git-am.sh
@@ -509,7 +509,11 @@ then
                git rerere clear
                if safe_to_abort
                then
-                       git read-tree --reset -u HEAD ORIG_HEAD
+                       head_tree=$(git rev-parse --verify -q HEAD || echo $empty_tree) &&
+                       git read-tree --reset -u $head_tree $head_tree &&
+                       index_tree=$(git write-tree) &&
+                       orig_head=$(git rev-parse --verify -q ORIG_HEAD || echo $empty_tree) &&
+                       git read-tree -m -u $index_tree $orig_head
                        git reset ORIG_HEAD
                fi
                rm -fr "$dotest"

diff --git a/t/t4151-am-abort.sh b/t/t4151-am-abort.sh
index 2a7c5247f9eb1083d615a8ff96fdaf904a3e8443..e61be631143ca0039c50e0f2d7656cb17d4a49c9 100755 (executable)
--- a/t/t4151-am-abort.sh
+++ b/t/t4151-am-abort.sh
@@ -70,6 +70,17 @@ test_expect_success 'am -3 --skip removes otherfile-4' '
        test 4 = "$(cat otherfile-4)" &&
        git am --skip &&
        test_cmp_rev initial HEAD &&
+       test -z "$(git ls-files -u)" &&
+       test_path_is_missing otherfile-4
+'
+
+test_expect_success 'am -3 --abort removes otherfile-4' '
+       git reset --hard initial &&
+       test_must_fail git am -3 0003-*.patch &&
+       test 3 -eq $(git ls-files -u | wc -l) &&
+       test 4 = "$(cat otherfile-4)" &&
+       git am --abort &&
+       test_cmp_rev initial HEAD &&
        test -z $(git ls-files -u) &&
        test_path_is_missing otherfile-4
 '
@@ -102,4 +113,16 @@ test_expect_success 'am -3 --skip clears index on unborn branch' '
        test_path_is_missing tmpfile
 '
 
+test_expect_success 'am -3 --abort removes otherfile-4 on unborn branch' '
+       git checkout -f --orphan orphan &&
+       git reset &&
+       rm -f otherfile-4 file-1 &&
+       test_must_fail git am -3 0003-*.patch &&
+       test 2 -eq $(git ls-files -u | wc -l) &&
+       test 4 = "$(cat otherfile-4)" &&
+       git am --abort &&
+       test -z "$(git ls-files -u)" &&
+       test_path_is_missing otherfile-4
+'
+
 test_done