Merge branch 'en/merge-restore-to-pristine'

When "git merge" finds that it cannot perform a merge, it should
restore the working tree to the state before the command was
initiated, but in some corner cases it didn't.

* en/merge-restore-to-pristine:
  merge: do not exit restore_state() prematurely
  merge: ensure we can actually restore pre-merge state
  merge: make restore_state() restore staged state too
  merge: fix save_state() to work when there are stat-dirty files
  merge: do not abort early if one strategy fails to handle the merge
  merge: abort if index does not match HEAD for trivial merges
  merge-resolve: abort if index does not match HEAD
  merge-ort-wrappers: make printed message match the one from recursive

4 files changed, 99 insertions, 1 deletions

diff --git a/t/t6402-merge-rename.sh b/t/t6402-merge-rename.sh
index 3a32b1a..772238e 100755
--- a/t/t6402-merge-rename.sh
+++ b/t/t6402-merge-rename.sh
@@ -210,7 +210,7 @@ test_expect_success 'updated working tree file should prevent the merge' '
 	echo >>M one line addition &&
 	cat M >M.saved &&
 	git update-index M &&
-	test_expect_code 128 git pull --no-rebase . yellow &&
+	test_expect_code 2 git pull --no-rebase . yellow &&
 	test_cmp M M.saved &&
 	rm -f M.saved
 '
diff --git a/t/t6424-merge-unrelated-index-changes.sh b/t/t6424-merge-unrelated-index-changes.sh
index b6e424a..a61f20c 100755
--- a/t/t6424-merge-unrelated-index-changes.sh
+++ b/t/t6424-merge-unrelated-index-changes.sh
@@ -114,6 +114,39 @@ test_expect_success 'resolve, non-trivial' '
 	test_path_is_missing .git/MERGE_HEAD
 '
 
+test_expect_success 'resolve, trivial, related file removed' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	git rm a &&
+	test_path_is_missing a &&
+
+	test_must_fail git merge -s resolve C^0 &&
+
+	test_path_is_missing a &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_expect_success 'resolve, non-trivial, related file removed' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	git rm a &&
+	test_path_is_missing a &&
+
+	# We also ask for recursive in order to turn off the "allow_trivial"
+	# setting in builtin/merge.c, and ensure that resolve really does
+	# correctly fail the merge (I guess this also tests that recursive
+	# correctly fails the merge, but the main thing we are attempting
+	# to test here is resolve and are just using the side effect of
+	# adding recursive to ensure that resolve is actually tested rather
+	# than the trivial merge codepath)
+	test_must_fail git merge -s resolve -s recursive D^0 &&
+
+	test_path_is_missing a &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
 test_expect_success 'recursive' '
 	git reset --hard &&
 	git checkout B^0 &&
@@ -242,4 +275,36 @@ test_expect_success 'subtree' '
 	test_path_is_missing .git/MERGE_HEAD
 '
 
+test_expect_success 'avoid failure due to stat-dirty files' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	# Make "a" be stat-dirty
+	test-tool chmtime =+1 a &&
+
+	# stat-dirty file should not prevent stash creation in builtin/merge.c
+	git merge -s resolve -s recursive D^0
+'
+
+test_expect_success 'with multiple strategies, recursive or ort failure do not early abort' '
+	git reset --hard &&
+	git checkout B^0 &&
+
+	test_seq 0 10 >a &&
+	git add a &&
+	git rev-parse :a >expect &&
+
+	sane_unset GIT_TEST_MERGE_ALGORITHM &&
+	test_must_fail git merge -s recursive -s ort -s octopus C^0 >output 2>&1 &&
+
+	grep "Trying merge strategy recursive..." output &&
+	grep "Trying merge strategy ort..." output &&
+	grep "Trying merge strategy octopus..." output &&
+	grep "No merge strategy handled the merge." output &&
+
+	# Changes to "a" should remain staged
+	git rev-parse :a >actual &&
+	test_cmp expect actual
+'
+
 test_done
diff --git a/t/t6439-merge-co-error-msgs.sh b/t/t6439-merge-co-error-msgs.sh
index 5bfb027..52cf0c8 100755
--- a/t/t6439-merge-co-error-msgs.sh
+++ b/t/t6439-merge-co-error-msgs.sh
@@ -47,6 +47,7 @@ test_expect_success 'untracked files overwritten by merge (fast and non-fast for
 		export GIT_MERGE_VERBOSITY &&
 		test_must_fail git merge branch 2>out2
 	) &&
+	echo "Merge with strategy ${GIT_TEST_MERGE_ALGORITHM:-ort} failed." >>expect &&
 	test_cmp out2 expect &&
 	git reset --hard HEAD^
 '
diff --git a/t/t7607-merge-state.sh b/t/t7607-merge-state.sh
new file mode 100755
index 0000000..89a62ac
--- /dev/null
+++ b/t/t7607-merge-state.sh
@@ -0,0 +1,32 @@
+#!/bin/sh
+
+test_description="Test that merge state is as expected after failed merge"
+
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+. ./test-lib.sh
+
+test_expect_success 'Ensure we restore original state if no merge strategy handles it' '
+	test_commit --no-tag "Initial" base base &&
+
+	for b in branch1 branch2 branch3
+	do
+		git checkout -b $b main &&
+		test_commit --no-tag "Change on $b" base $b || return 1
+	done &&
+
+	git checkout branch1 &&
+	# This is a merge that octopus cannot handle.  Note, that it does not
+	# just hit conflicts, it completely fails and says that it cannot
+	# handle this type of merge.
+	test_expect_code 2 git merge branch2 branch3 >output 2>&1 &&
+	grep "fatal: merge program failed" output &&
+	grep "Should not be doing an octopus" output &&
+
+	# Make sure we did not leave stray changes around when no appropriate
+	# merge strategy was found
+	git diff --exit-code --name-status &&
+	test_path_is_missing .git/MERGE_HEAD
+'
+
+test_done