Merge branch 'jc/better-conflict-resolution'

* jc/better-conflict-resolution:
  Fix AsciiDoc errors in merge documentation
  git-merge documentation: describe how conflict is presented
  checkout --conflict=<style>: recreate merge in a non-default style
  checkout -m: recreate merge when checking out of unmerged index
  git-merge-recursive: learn to honor merge.conflictstyle
  merge.conflictstyle: choose between "merge" and "diff3 -m" styles
  rerere: understand "diff3 -m" style conflicts with the original
  rerere.c: use symbolic constants to keep track of parsing states
  xmerge.c: "diff3 -m" style clips merge reduction level to EAGER or less
  xmerge.c: minimum readability fixups
  xdiff-merge: optionally show conflicts in "diff3 -m" style
  xdl_fill_merge_buffer(): separate out a too deeply nested function
  checkout --ours/--theirs: allow checking out one side of a conflicting merge
  checkout -f: allow ignoring unmerged paths when checking out of the index

Conflicts:
	Documentation/git-checkout.txt
	builtin-checkout.c
	builtin-merge-recursive.c
	t/t7201-co.sh

2 files changed, 165 insertions, 2 deletions

diff --git a/t/t6023-merge-file.sh b/t/t6023-merge-file.sh
index 5e18d68c9..f8942bc89 100755
--- a/t/t6023-merge-file.sh
+++ b/t/t6023-merge-file.sh
@@ -161,4 +161,48 @@ test_expect_success 'ZEALOUS_ALNUM' '
 
 '
 
+cat >expect <<\EOF
+Dominus regit me,
+<<<<<<< new8.txt
+et nihil mihi deerit;
+
+
+
+
+In loco pascuae ibi me collocavit;
+super aquam refectionis educavit me.
+|||||||
+et nihil mihi deerit.
+In loco pascuae ibi me collocavit,
+super aquam refectionis educavit me;
+=======
+et nihil mihi deerit,
+
+
+
+
+In loco pascuae ibi me collocavit --
+super aquam refectionis educavit me,
+>>>>>>> new9.txt
+animam meam convertit,
+deduxit me super semitas jusitiae,
+propter nomen suum.
+Nam et si ambulavero in medio umbrae mortis,
+non timebo mala, quoniam TU mecum es:
+virga tua et baculus tuus ipsa me consolata sunt.
+EOF
+
+test_expect_success '"diff3 -m" style output (1)' '
+	test_must_fail git merge-file -p --diff3 \
+		new8.txt new5.txt new9.txt >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '"diff3 -m" style output (2)' '
+	git config merge.conflictstyle diff3 &&
+	test_must_fail git merge-file -p \
+		new8.txt new5.txt new9.txt >actual &&
+	test_cmp expect actual
+'
+
 test_done
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 62d73f934..82769b89f 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -369,7 +369,7 @@ test_expect_success \
     'checkout with --track, but without -b, fails with too short tracked name' '
     test_must_fail git checkout --track renamer'
 
-test_expect_success 'checkout an unmerged path should fail' '
+setup_conflicting_index () {
 	rm -f .git/index &&
 	O=$(echo original | git hash-object -w --stdin) &&
 	A=$(echo ourside | git hash-object -w --stdin) &&
@@ -380,7 +380,11 @@ test_expect_success 'checkout an unmerged path should fail' '
 		echo "100644 $A 2	file" &&
 		echo "100644 $B 3	file" &&
 		echo "100644 $A 0	filf"
-	) | git update-index --index-info &&
+	) | git update-index --index-info
+}
+
+test_expect_success 'checkout an unmerged path should fail' '
+	setup_conflicting_index &&
 	echo "none of the above" >sample &&
 	cat sample >fild &&
 	cat sample >file &&
@@ -391,6 +395,121 @@ test_expect_success 'checkout an unmerged path should fail' '
 	test_cmp sample file
 '
 
+test_expect_success 'checkout with an unmerged path can be ignored' '
+	setup_conflicting_index &&
+	echo "none of the above" >sample &&
+	echo ourside >expect &&
+	cat sample >fild &&
+	cat sample >file &&
+	cat sample >filf &&
+	git checkout -f fild file filf &&
+	test_cmp expect fild &&
+	test_cmp expect filf &&
+	test_cmp sample file
+'
+
+test_expect_success 'checkout unmerged stage' '
+	setup_conflicting_index &&
+	echo "none of the above" >sample &&
+	echo ourside >expect &&
+	cat sample >fild &&
+	cat sample >file &&
+	cat sample >filf &&
+	git checkout --ours . &&
+	test_cmp expect fild &&
+	test_cmp expect filf &&
+	test_cmp expect file &&
+	git checkout --theirs file &&
+	test ztheirside = "z$(cat file)"
+'
+
+test_expect_success 'checkout with --merge' '
+	setup_conflicting_index &&
+	echo "none of the above" >sample &&
+	echo ourside >expect &&
+	cat sample >fild &&
+	cat sample >file &&
+	cat sample >filf &&
+	git checkout -m -- fild file filf &&
+	(
+		echo "<<<<<<< ours"
+		echo ourside
+		echo "======="
+		echo theirside
+		echo ">>>>>>> theirs"
+	) >merged &&
+	test_cmp expect fild &&
+	test_cmp expect filf &&
+	test_cmp merged file
+'
+
+test_expect_success 'checkout with --merge, in diff3 -m style' '
+	git config merge.conflictstyle diff3 &&
+	setup_conflicting_index &&
+	echo "none of the above" >sample &&
+	echo ourside >expect &&
+	cat sample >fild &&
+	cat sample >file &&
+	cat sample >filf &&
+	git checkout -m -- fild file filf &&
+	(
+		echo "<<<<<<< ours"
+		echo ourside
+		echo "|||||||"
+		echo original
+		echo "======="
+		echo theirside
+		echo ">>>>>>> theirs"
+	) >merged &&
+	test_cmp expect fild &&
+	test_cmp expect filf &&
+	test_cmp merged file
+'
+
+test_expect_success 'checkout --conflict=merge, overriding config' '
+	git config merge.conflictstyle diff3 &&
+	setup_conflicting_index &&
+	echo "none of the above" >sample &&
+	echo ourside >expect &&
+	cat sample >fild &&
+	cat sample >file &&
+	cat sample >filf &&
+	git checkout --conflict=merge -- fild file filf &&
+	(
+		echo "<<<<<<< ours"
+		echo ourside
+		echo "======="
+		echo theirside
+		echo ">>>>>>> theirs"
+	) >merged &&
+	test_cmp expect fild &&
+	test_cmp expect filf &&
+	test_cmp merged file
+'
+
+test_expect_success 'checkout --conflict=diff3' '
+	git config --unset merge.conflictstyle
+	setup_conflicting_index &&
+	echo "none of the above" >sample &&
+	echo ourside >expect &&
+	cat sample >fild &&
+	cat sample >file &&
+	cat sample >filf &&
+	git checkout --conflict=diff3 -- fild file filf &&
+	(
+		echo "<<<<<<< ours"
+		echo ourside
+		echo "|||||||"
+		echo original
+		echo "======="
+		echo theirside
+		echo ">>>>>>> theirs"
+	) >merged &&
+	test_cmp expect fild &&
+	test_cmp expect filf &&
+	test_cmp merged file
+'
+
 test_expect_success 'failing checkout -b should not break working tree' '
 	git reset --hard master &&
 	git symbolic-ref HEAD refs/heads/master &&