git-merge-file: do not add LF at EOF while applying unrelated change

If 'current-file' does not contain LF at EOF, and change between
'base-file' and 'other-file' does not change any line close to EOF, the
3-way merge should not add LF to EOF.  This is what 'diff3 -m' does, and
seems to be a reasonable expectation.

The change which introduced the behavior is cd1d61c. It always calls
function xdl_recs_copy() for sides with add_nl == 1. In fact, it looks
like the only case when this is needed is when 2 files are being
union-merged, and they do not have LF at EOF (strictly speaking, the
first of them).

Add tests:
* "merge without conflict (missing LF at EOF, away from change in the
other file)" and "merge does not add LF away of change", to demonstrate
the changed behavior.
* "conflict at EOF without LF resolved by --union", to verify that the
union-merge at the end inerts newline between versions.
* some more tests which I felt like not covering the functionality well

Signed-off-by: Max Kirillov <max@max630.net>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6023-merge-file.sh

@@ -83,6 +83,23 @@ test_expect_failure "merge without conflict (missing LF at EOF)" \
 test_expect_failure "merge result added missing LF" \
 	"test_cmp test.txt test2.txt"
 
+cp new4.txt test3.txt
+test_expect_success "merge without conflict (missing LF at EOF, away from change in the other file)" \
+	"git merge-file --quiet test3.txt new2.txt new3.txt"
+
+cat > expect.txt << EOF
+DOMINUS regit me,
+et nihil mihi deerit.
+In loco pascuae ibi me collocavit,
+super aquam refectionis educavit me;
+animam meam convertit,
+deduxit me super semitas jusitiae,
+EOF
+printf "propter nomen suum." >> expect.txt
+
+test_expect_success "merge does not add LF away of change" \
+	"test_cmp test3.txt expect.txt"
+
 cp test.txt backup.txt
 test_expect_success "merge with conflicts" \
 	"test_must_fail git merge-file test.txt orig.txt new3.txt"
@@ -107,6 +124,55 @@ EOF
 test_expect_success "expected conflict markers" "test_cmp test.txt expect.txt"
 
 cp backup.txt test.txt
+
+cat > expect.txt << EOF
+Dominus regit me, et nihil mihi deerit.
+In loco pascuae ibi me collocavit,
+super aquam refectionis educavit me;
+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 "merge conflicting with --ours" \
+	"git merge-file --ours test.txt orig.txt new3.txt && test_cmp test.txt expect.txt"
+cp backup.txt test.txt
+
+cat > expect.txt << EOF
+DOMINUS regit me,
+et nihil mihi deerit.
+In loco pascuae ibi me collocavit,
+super aquam refectionis educavit me;
+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 "merge conflicting with --theirs" \
+	"git merge-file --theirs test.txt orig.txt new3.txt && test_cmp test.txt expect.txt"
+cp backup.txt test.txt
+
+cat > expect.txt << EOF
+Dominus regit me, et nihil mihi deerit.
+DOMINUS regit me,
+et nihil mihi deerit.
+In loco pascuae ibi me collocavit,
+super aquam refectionis educavit me;
+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 "merge conflicting with --union" \
+	"git merge-file --union test.txt orig.txt new3.txt && test_cmp test.txt expect.txt"
+cp backup.txt test.txt
+
 test_expect_success "merge with conflicts, using -L" \
 	"test_must_fail git merge-file -L 1 -L 2 test.txt orig.txt new3.txt"
 
@@ -260,4 +326,23 @@ test_expect_success 'marker size' '
 	test_cmp expect actual
 '
 
+printf "line1\nline2\nline3" >nolf-orig.txt
+printf "line1\nline2\nline3x" >nolf-diff1.txt
+printf "line1\nline2\nline3y" >nolf-diff2.txt
+
+test_expect_success 'conflict at EOF without LF resolved by --ours' \
+	'git merge-file -p --ours nolf-diff1.txt nolf-orig.txt nolf-diff2.txt >output.txt &&
+	 printf "line1\nline2\nline3x" >expect.txt &&
+	 test_cmp expect.txt output.txt'
+
+test_expect_success 'conflict at EOF without LF resolved by --theirs' \
+	'git merge-file -p --theirs nolf-diff1.txt nolf-orig.txt nolf-diff2.txt >output.txt &&
+	 printf "line1\nline2\nline3y" >expect.txt &&
+	 test_cmp expect.txt output.txt'
+
+test_expect_success 'conflict at EOF without LF resolved by --union' \
+	'git merge-file -p --union nolf-diff1.txt nolf-orig.txt nolf-diff2.txt >output.txt &&
+	 printf "line1\nline2\nline3x\nline3y" >expect.txt &&
+	 test_cmp expect.txt output.txt'
+
 test_done

xdiff/xmerge.c

@@ -245,11 +245,11 @@ static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
 					      dest ? dest + size : NULL);
 			/* Postimage from side #1 */
 			if (m->mode & 1)
-				size += xdl_recs_copy(xe1, m->i1, m->chg1, 1,
+				size += xdl_recs_copy(xe1, m->i1, m->chg1, (m->mode & 2),
 						      dest ? dest + size : NULL);
 			/* Postimage from side #2 */
 			if (m->mode & 2)
-				size += xdl_recs_copy(xe2, m->i2, m->chg2, 1,
+				size += xdl_recs_copy(xe2, m->i2, m->chg2, 0,
 						      dest ? dest + size : NULL);
 		} else
 			continue;