[PATCH] Fix '\ No newline...' annotation in rewrite diffs

[Adam Butcher <dev.lists@jessamine.co.uk>]

When a file that ends with an incomplete line is expressed as a
complete rewrite with the -B option, git diff incorrectly appends the
incomplete line indicator "\ No newline at end of file" after such a
line, rather than writing it on a line of its own (the output codepath
for normal output without -B does not have this problem).  Add a LF
after the incomplete line before writing the "\ No newline ..." out
to fix this.

Add a couple of tests to confirm that the indicator comment is
generated on its own line in both plain diff and rewrite mode.

Signed-off-by: Adam Butcher <dev.lists@jessamine.co.uk>
---

Updates:

  - replace commit msg with revised suggestion from Junio
  - remove hardcoded 'No newline...' in tests and simplify

 diff.c                  |  1 +
 t/t4022-diff-rewrite.sh | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/diff.c b/diff.c
index 1a594df..f333de8 100644
--- a/diff.c
+++ b/diff.c
@@ -574,6 +574,7 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 	if (!endp) {
 		const char *plain = diff_get_color(ecb->color_diff,
 						   DIFF_PLAIN);
+		putc('\n', ecb->opt->file);
 		emit_line_0(ecb->opt, plain, reset, '\\',
 			    nneof, strlen(nneof));
 	}
diff --git a/t/t4022-diff-rewrite.sh b/t/t4022-diff-rewrite.sh
index c00a94b..05ac3e9 100755
--- a/t/t4022-diff-rewrite.sh
+++ b/t/t4022-diff-rewrite.sh
@@ -66,5 +66,38 @@ test_expect_success 'suppress deletion diff with -B -D' '
 	grep -v "Linus Torvalds" actual
 '
 
+test_expect_success 'generate initial "no newline at eof" sequence file and commit' '
+
+	test_seq 1 99 >seq &&
+	printf 100 >>seq &&
+	git add seq &&
+	git commit seq -m seq
+'
+
+test_expect_success 'rewrite the middle 90% of sequence file and terminate with newline' '
+
+	test_seq 1 5 >seq &&
+	test_seq 9331 9420 >>seq &&
+	test_seq 96 100 >>seq
+'
+
+test_expect_success 'confirm that sequence file is considered a rewrite' '
+
+	git diff -B seq >res &&
+	grep "dissimilarity index" res
+'
+
+test_expect_success 'no newline at eof is on its own line without -B' '
+
+	git diff seq >res &&
+	grep "^\\\\ " res && ! grep "^..*\\\\ " res
+'
+
+test_expect_success 'no newline at eof is on its own line with -B' '
+
+	git diff -B seq >res &&
+	grep "^\\\\ " res && ! grep "^..*\\\\ " res
+'
+
 test_done
 
-- 
1.7.11.msysgit.1.1.gf0affa1