Merge branch 'jn/merge-diff3-label'

* jn/merge-diff3-label:
  merge-recursive: add a label for ancestor
  cherry-pick, revert: add a label for ancestor
  revert: clarify label on conflict hunks
  compat: add mempcpy()
  checkout -m --conflict=diff3: add a label for ancestor
  merge_trees(): add ancestor label parameter for diff3-style output
  merge_file(): add comment explaining behavior wrt conflict style
  checkout --conflict=diff3: add a label for ancestor
  ll_merge(): add ancestor label parameter for diff3-style output
  merge-file --diff3: add a label for ancestor
  xdl_merge(): move file1 and file2 labels to xmparam structure
  xdl_merge(): add optional ancestor label to diff3-style output
  tests: document cherry-pick behavior in face of conflicts
  tests: document format of conflicts from checkout -m

Conflicts:
	builtin/revert.c

3 files changed, 263 insertions, 8 deletions

diff --git a/t/t3507-cherry-pick-conflict.sh b/t/t3507-cherry-pick-conflict.sh
new file mode 100644
index 0000000..e25cf80
--- /dev/null
+++ b/t/t3507-cherry-pick-conflict.sh
@@ -0,0 +1,198 @@
+#!/bin/sh
+
+test_description='test cherry-pick and revert with conflicts
+
+  -
+  + picked: rewrites foo to c
+  + base: rewrites foo to b
+  + initial: writes foo as a, unrelated as unrelated
+
+'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+
+	echo unrelated >unrelated &&
+	git add unrelated &&
+	test_commit initial foo a &&
+	test_commit base foo b &&
+	test_commit picked foo c &&
+	git config advice.detachedhead false
+
+'
+
+test_expect_success 'failed cherry-pick does not advance HEAD' '
+
+	git checkout -f initial^0 &&
+	git read-tree -u --reset HEAD &&
+	git clean -d -f -f -q -x &&
+
+	git update-index --refresh &&
+	git diff-index --exit-code HEAD &&
+
+	head=$(git rev-parse HEAD) &&
+	test_must_fail git cherry-pick picked &&
+	newhead=$(git rev-parse HEAD) &&
+
+	test "$head" = "$newhead"
+'
+
+test_expect_success 'failed cherry-pick produces dirty index' '
+
+	git checkout -f initial^0 &&
+	git read-tree -u --reset HEAD &&
+	git clean -d -f -f -q -x &&
+
+	git update-index --refresh &&
+	git diff-index --exit-code HEAD &&
+
+	test_must_fail git cherry-pick picked &&
+
+	test_must_fail git update-index --refresh -q &&
+	test_must_fail git diff-index --exit-code HEAD
+'
+
+test_expect_success 'failed cherry-pick registers participants in index' '
+
+	git read-tree -u --reset HEAD &&
+	git clean -d -f -f -q -x &&
+	{
+		git checkout base -- foo &&
+		git ls-files --stage foo &&
+		git checkout initial -- foo &&
+		git ls-files --stage foo &&
+		git checkout picked -- foo &&
+		git ls-files --stage foo
+	} > stages &&
+	sed "
+		1 s/ 0	/ 1	/
+		2 s/ 0	/ 2	/
+		3 s/ 0	/ 3	/
+	" < stages > expected &&
+	git checkout -f initial^0 &&
+
+	git update-index --refresh &&
+	git diff-index --exit-code HEAD &&
+
+	test_must_fail git cherry-pick picked &&
+	git ls-files --stage --unmerged > actual &&
+
+	test_cmp expected actual
+'
+
+test_expect_success 'failed cherry-pick describes conflict in work tree' '
+
+	git checkout -f initial^0 &&
+	git read-tree -u --reset HEAD &&
+	git clean -d -f -f -q -x &&
+	cat <<-EOF > expected &&
+	<<<<<<< HEAD
+	a
+	=======
+	c
+	>>>>>>> objid picked
+	EOF
+
+	git update-index --refresh &&
+	git diff-index --exit-code HEAD &&
+
+	test_must_fail git cherry-pick picked &&
+
+	sed "s/[a-f0-9]*\.\.\./objid/" foo > actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'diff3 -m style' '
+
+	git config merge.conflictstyle diff3 &&
+	git checkout -f initial^0 &&
+	git read-tree -u --reset HEAD &&
+	git clean -d -f -f -q -x &&
+	cat <<-EOF > expected &&
+	<<<<<<< HEAD
+	a
+	||||||| parent of objid picked
+	b
+	=======
+	c
+	>>>>>>> objid picked
+	EOF
+
+	git update-index --refresh &&
+	git diff-index --exit-code HEAD &&
+
+	test_must_fail git cherry-pick picked &&
+
+	sed "s/[a-f0-9]*\.\.\./objid/" foo > actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'revert also handles conflicts sanely' '
+
+	git config --unset merge.conflictstyle &&
+	git read-tree -u --reset HEAD &&
+	git clean -d -f -f -q -x &&
+	cat <<-EOF > expected &&
+	<<<<<<< HEAD
+	a
+	=======
+	b
+	>>>>>>> parent of objid picked
+	EOF
+	{
+		git checkout picked -- foo &&
+		git ls-files --stage foo &&
+		git checkout initial -- foo &&
+		git ls-files --stage foo &&
+		git checkout base -- foo &&
+		git ls-files --stage foo
+	} > stages &&
+	sed "
+		1 s/ 0	/ 1	/
+		2 s/ 0	/ 2	/
+		3 s/ 0	/ 3	/
+	" < stages > expected-stages &&
+	git checkout -f initial^0 &&
+
+	git update-index --refresh &&
+	git diff-index --exit-code HEAD &&
+
+	head=$(git rev-parse HEAD) &&
+	test_must_fail git revert picked &&
+	newhead=$(git rev-parse HEAD) &&
+	git ls-files --stage --unmerged > actual-stages &&
+
+	test "$head" = "$newhead" &&
+	test_must_fail git update-index --refresh -q &&
+	test_must_fail git diff-index --exit-code HEAD &&
+	test_cmp expected-stages actual-stages &&
+	sed "s/[a-f0-9]*\.\.\./objid/" foo > actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'revert conflict, diff3 -m style' '
+	git config merge.conflictstyle diff3 &&
+	git checkout -f initial^0 &&
+	git read-tree -u --reset HEAD &&
+	git clean -d -f -f -q -x &&
+	cat <<-EOF > expected &&
+	<<<<<<< HEAD
+	a
+	||||||| objid picked
+	c
+	=======
+	b
+	>>>>>>> parent of objid picked
+	EOF
+
+	git update-index --refresh &&
+	git diff-index --exit-code HEAD &&
+
+	test_must_fail git revert picked &&
+
+	sed "s/[a-f0-9]*\.\.\./objid/" foo > actual &&
+	test_cmp expected actual
+'
+
+test_done
diff --git a/t/t6023-merge-file.sh b/t/t6023-merge-file.sh
index 5034dd1..d486d73 100755
--- a/t/t6023-merge-file.sh
+++ b/t/t6023-merge-file.sh
@@ -181,7 +181,7 @@ et nihil mihi deerit;
 
 In loco pascuae ibi me collocavit;
 super aquam refectionis educavit me.
-|||||||
+||||||| new5.txt
 et nihil mihi deerit.
 In loco pascuae ibi me collocavit,
 super aquam refectionis educavit me;
@@ -225,7 +225,7 @@ et nihil mihi deerit;
 
 In loco pascuae ibi me collocavit;
 super aquam refectionis educavit me.
-||||||||||
+|||||||||| new5.txt
 et nihil mihi deerit.
 In loco pascuae ibi me collocavit,
 super aquam refectionis educavit me;
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index d20ed61..1337fa5 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -11,10 +11,12 @@ Test switching across them.
   ! [master] Initial A one, A two
    * [renamer] Renamer R one->uno, M two
     ! [side] Side M one, D two, A three
-  ---
-    + [side] Side M one, D two, A three
-   *  [renamer] Renamer R one->uno, M two
-  +*+ [master] Initial A one, A two
+     ! [simple] Simple D one, M two
+  ----
+     + [simple] Simple D one, M two
+    +  [side] Side M one, D two, A three
+   *   [renamer] Renamer R one->uno, M two
+  +*++ [master] Initial A one, A two
 
 '
 
@@ -52,6 +54,11 @@ test_expect_success setup '
 	git update-index --add --remove one two three &&
 	git commit -m "Side M one, D two, A three" &&
 
+	git checkout -b simple master &&
+	rm -f one &&
+	fill a c e > two &&
+	git commit -a -m "Simple D one, M two" &&
+
 	git checkout master
 '
 
@@ -166,6 +173,56 @@ test_expect_success 'checkout -m with merge conflict' '
 	! test -s current
 '
 
+test_expect_success 'format of merge conflict from checkout -m' '
+
+	git checkout -f master && git clean -f &&
+
+	fill b d > two &&
+	git checkout -m simple &&
+
+	git ls-files >current &&
+	fill same two two two >expect &&
+	test_cmp current expect &&
+
+	cat <<-EOF >expect &&
+	<<<<<<< simple
+	a
+	c
+	e
+	=======
+	b
+	d
+	>>>>>>> local
+	EOF
+	test_cmp two expect
+'
+
+test_expect_success 'checkout --merge --conflict=diff3 <branch>' '
+
+	git checkout -f master && git reset --hard && git clean -f &&
+
+	fill b d > two &&
+	git checkout --merge --conflict=diff3 simple &&
+
+	cat <<-EOF >expect &&
+	<<<<<<< simple
+	a
+	c
+	e
+	||||||| master
+	a
+	b
+	c
+	d
+	e
+	=======
+	b
+	d
+	>>>>>>> local
+	EOF
+	test_cmp two expect
+'
+
 test_expect_success 'checkout to detach HEAD (with advice declined)' '
 
 	git config advice.detachedHead false &&
@@ -481,7 +538,7 @@ test_expect_success 'checkout with --merge, in diff3 -m style' '
 	(
 		echo "<<<<<<< ours"
 		echo ourside
-		echo "|||||||"
+		echo "||||||| base"
 		echo original
 		echo "======="
 		echo theirside
@@ -525,7 +582,7 @@ test_expect_success 'checkout --conflict=diff3' '
 	(
 		echo "<<<<<<< ours"
 		echo ourside
-		echo "|||||||"
+		echo "||||||| base"
 		echo original
 		echo "======="
 		echo theirside