Merge branch 'js/xmerge-marker-eol' into maint

The low-level merge machinery has been taught to use CRLF line
termination when inserting conflict markers to merged contents that
are themselves CRLF line-terminated.

* js/xmerge-marker-eol:
  merge-file: ensure that conflict sections match eol style
  merge-file: let conflict markers match end-of-line style of the context

2 files changed, 93 insertions, 18 deletions

diff --git a/t/t6023-merge-file.sh b/t/t6023-merge-file.sh
index 190ee903cf..20aee43f95 100755
--- a/t/t6023-merge-file.sh
+++ b/t/t6023-merge-file.sh
@@ -346,4 +346,17 @@ test_expect_success 'conflict at EOF without LF resolved by --union' \
 	 printf "line1\nline2\nline3x\nline3y" >expect.txt &&
 	 test_cmp expect.txt output.txt'
 
+test_expect_success 'conflict sections match existing line endings' '
+	printf "1\\r\\n2\\r\\n3" >crlf-orig.txt &&
+	printf "1\\r\\n2\\r\\n4" >crlf-diff1.txt &&
+	printf "1\\r\\n2\\r\\n5" >crlf-diff2.txt &&
+	test_must_fail git -c core.eol=crlf merge-file -p \
+		crlf-diff1.txt crlf-orig.txt crlf-diff2.txt >crlf.txt &&
+	test $(tr "\015" Q <crlf.txt | grep "^[<=>].*Q$" | wc -l) = 3 &&
+	test $(tr "\015" Q <crlf.txt | grep "[345]Q$" | wc -l) = 3 &&
+	test_must_fail git -c core.eol=crlf merge-file -p \
+		nolf-diff1.txt nolf-orig.txt nolf-diff2.txt >nolf.txt &&
+	test $(tr "\015" Q <nolf.txt | grep "^[<=>].*Q$" | wc -l) = 0
+'
+
 test_done
diff --git a/xdiff/xmerge.c b/xdiff/xmerge.c
index 625198e058..d98f430c91 100644
--- a/xdiff/xmerge.c
+++ b/xdiff/xmerge.c
@@ -109,7 +109,7 @@ static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,
 	return 0;
 }
 
-static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add_nl, char *dest)
+static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
 {
 	xrecord_t **recs;
 	int size = 0;
@@ -125,6 +125,12 @@ static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add
 	if (add_nl) {
 		i = recs[count - 1]->size;
 		if (i == 0 || recs[count - 1]->ptr[i - 1] != '\n') {
+			if (needs_cr) {
+				if (dest)
+					dest[size] = '\r';
+				size++;
+			}
+
 			if (dest)
 				dest[size] = '\n';
 			size++;
@@ -133,14 +139,58 @@ static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add
 	return size;
 }
 
-static int xdl_recs_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
+static int xdl_recs_copy(xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
+{
+	return xdl_recs_copy_0(0, xe, i, count, needs_cr, add_nl, dest);
+}
+
+static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
+{
+	return xdl_recs_copy_0(1, xe, i, count, needs_cr, add_nl, dest);
+}
+
+/*
+ * Returns 1 if the i'th line ends in CR/LF (if it is the last line and
+ * has no eol, the preceding line, if any), 0 if it ends in LF-only, and
+ * -1 if the line ending cannot be determined.
+ */
+static int is_eol_crlf(xdfile_t *file, int i)
 {
-	return xdl_recs_copy_0(0, xe, i, count, add_nl, dest);
+	long size;
+
+	if (i < file->nrec - 1)
+		/* All lines before the last *must* end in LF */
+		return (size = file->recs[i]->size) > 1 &&
+			file->recs[i]->ptr[size - 2] == '\r';
+	if (!file->nrec)
+		/* Cannot determine eol style from empty file */
+		return -1;
+	if ((size = file->recs[i]->size) &&
+			file->recs[i]->ptr[size - 1] == '\n')
+		/* Last line; ends in LF; Is it CR/LF? */
+		return size > 1 &&
+			file->recs[i]->ptr[size - 2] == '\r';
+	if (!i)
+		/* The only line has no eol */
+		return -1;
+	/* Determine eol from second-to-last line */
+	return (size = file->recs[i - 1]->size) > 1 &&
+		file->recs[i - 1]->ptr[size - 2] == '\r';
 }
 
-static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
+static int is_cr_needed(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m)
 {
-	return xdl_recs_copy_0(1, xe, i, count, add_nl, dest);
+	int needs_cr;
+
+	/* Match post-images' preceding, or first, lines' end-of-line style */
+	needs_cr = is_eol_crlf(&xe1->xdf2, m->i1 ? m->i1 - 1 : 0);
+	if (needs_cr)
+		needs_cr = is_eol_crlf(&xe2->xdf2, m->i2 ? m->i2 - 1 : 0);
+	/* Look at pre-image's first line, unless we already settled on LF */
+	if (needs_cr)
+		needs_cr = is_eol_crlf(&xe1->xdf1, 0);
+	/* If still undecided, use LF-only */
+	return needs_cr < 0 ? 0 : needs_cr;
 }
 
 static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
@@ -152,16 +202,17 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 	int marker1_size = (name1 ? strlen(name1) + 1 : 0);
 	int marker2_size = (name2 ? strlen(name2) + 1 : 0);
 	int marker3_size = (name3 ? strlen(name3) + 1 : 0);
+	int needs_cr = is_cr_needed(xe1, xe2, m);
 
 	if (marker_size <= 0)
 		marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
 
 	/* Before conflicting part */
-	size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
+	size += xdl_recs_copy(xe1, i, m->i1 - i, 0, 0,
 			      dest ? dest + size : NULL);
 
 	if (!dest) {
-		size += marker_size + 1 + marker1_size;
+		size += marker_size + 1 + needs_cr + marker1_size;
 	} else {
 		memset(dest + size, '<', marker_size);
 		size += marker_size;
@@ -170,17 +221,19 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 			memcpy(dest + size + 1, name1, marker1_size - 1);
 			size += marker1_size;
 		}
+		if (needs_cr)
+			dest[size++] = '\r';
 		dest[size++] = '\n';
 	}
 
 	/* Postimage from side #1 */
-	size += xdl_recs_copy(xe1, m->i1, m->chg1, 1,
+	size += xdl_recs_copy(xe1, m->i1, m->chg1, needs_cr, 1,
 			      dest ? dest + size : NULL);
 
 	if (style == XDL_MERGE_DIFF3) {
 		/* Shared preimage */
 		if (!dest) {
-			size += marker_size + 1 + marker3_size;
+			size += marker_size + 1 + needs_cr + marker3_size;
 		} else {
 			memset(dest + size, '|', marker_size);
 			size += marker_size;
@@ -189,25 +242,29 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 				memcpy(dest + size + 1, name3, marker3_size - 1);
 				size += marker3_size;
 			}
+			if (needs_cr)
+				dest[size++] = '\r';
 			dest[size++] = '\n';
 		}
-		size += xdl_orig_copy(xe1, m->i0, m->chg0, 1,
+		size += xdl_orig_copy(xe1, m->i0, m->chg0, needs_cr, 1,
 				      dest ? dest + size : NULL);
 	}
 
 	if (!dest) {
-		size += marker_size + 1;
+		size += marker_size + 1 + needs_cr;
 	} else {
 		memset(dest + size, '=', marker_size);
 		size += marker_size;
+		if (needs_cr)
+			dest[size++] = '\r';
 		dest[size++] = '\n';
 	}
 
 	/* Postimage from side #2 */
-	size += xdl_recs_copy(xe2, m->i2, m->chg2, 1,
+	size += xdl_recs_copy(xe2, m->i2, m->chg2, needs_cr, 1,
 			      dest ? dest + size : NULL);
 	if (!dest) {
-		size += marker_size + 1 + marker2_size;
+		size += marker_size + 1 + needs_cr + marker2_size;
 	} else {
 		memset(dest + size, '>', marker_size);
 		size += marker_size;
@@ -216,6 +273,8 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 			memcpy(dest + size + 1, name2, marker2_size - 1);
 			size += marker2_size;
 		}
+		if (needs_cr)
+			dest[size++] = '\r';
 		dest[size++] = '\n';
 	}
 	return size;
@@ -241,21 +300,24 @@ static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
 						  marker_size);
 		else if (m->mode & 3) {
 			/* Before conflicting part */
-			size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
+			size += xdl_recs_copy(xe1, i, m->i1 - i, 0, 0,
 					      dest ? dest + size : NULL);
 			/* Postimage from side #1 */
-			if (m->mode & 1)
-				size += xdl_recs_copy(xe1, m->i1, m->chg1, (m->mode & 2),
+			if (m->mode & 1) {
+				int needs_cr = is_cr_needed(xe1, xe2, m);
+
+				size += xdl_recs_copy(xe1, m->i1, m->chg1, needs_cr, (m->mode & 2),
 						      dest ? dest + size : NULL);
+			}
 			/* Postimage from side #2 */
 			if (m->mode & 2)
-				size += xdl_recs_copy(xe2, m->i2, m->chg2, 0,
+				size += xdl_recs_copy(xe2, m->i2, m->chg2, 0, 0,
 						      dest ? dest + size : NULL);
 		} else
 			continue;
 		i = m->i1 + m->chg1;
 	}
-	size += xdl_recs_copy(xe1, i, xe1->xdf2.nrec - i, 0,
+	size += xdl_recs_copy(xe1, i, xe1->xdf2.nrec - i, 0, 0,
 			      dest ? dest + size : NULL);
 	return size;
 }