diff: fix "git show -C -C" output when renaming a binary file

A bug was introduced in 3e97c7c6af
(No diff -b/-w output for all-whitespace changes, Nov 19 2009)
that made the lines:

  diff --git a/bar b/sub/bar
  similarity index 100%
  rename from bar
  rename to sub/bar

disappear from "git show -C -C" output when file bar is a binary
file.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -1596,6 +1596,7 @@ static void builtin_diff(const char *name_a,
 			 struct diff_filespec *one,
 			 struct diff_filespec *two,
 			 const char *xfrm_msg,
+			 int must_show_header,
 			 struct diff_options *o,
 			 int complete_rewrite)
 {
@@ -1647,16 +1648,19 @@ static void builtin_diff(const char *name_a,
 		strbuf_addf(&header, "%snew file mode %06o%s\n", set, two->mode, reset);
 		if (xfrm_msg && xfrm_msg[0])
 			strbuf_addf(&header, "%s%s%s\n", set, xfrm_msg, reset);
+		must_show_header = 1;
 	}
 	else if (lbl[1][0] == '/') {
 		strbuf_addf(&header, "%sdeleted file mode %06o%s\n", set, one->mode, reset);
 		if (xfrm_msg && xfrm_msg[0])
 			strbuf_addf(&header, "%s%s%s\n", set, xfrm_msg, reset);
+		must_show_header = 1;
 	}
 	else {
 		if (one->mode != two->mode) {
 			strbuf_addf(&header, "%sold mode %06o%s\n", set, one->mode, reset);
 			strbuf_addf(&header, "%snew mode %06o%s\n", set, two->mode, reset);
+			must_show_header = 1;
 		}
 		if (xfrm_msg && xfrm_msg[0])
 			strbuf_addf(&header, "%s%s%s\n", set, xfrm_msg, reset);
@@ -1687,8 +1691,11 @@ static void builtin_diff(const char *name_a,
 	      (diff_filespec_is_binary(two) && !textconv_two) )) {
 		/* Quite common confusing case */
 		if (mf1.size == mf2.size &&
-		    !memcmp(mf1.ptr, mf2.ptr, mf1.size))
+		    !memcmp(mf1.ptr, mf2.ptr, mf1.size)) {
+			if (must_show_header)
+				fprintf(o->file, "%s", header.buf);
 			goto free_ab_and_return;
+		}
 		fprintf(o->file, "%s", header.buf);
 		strbuf_reset(&header);
 		if (DIFF_OPT_TST(o, BINARY))
@@ -1706,7 +1713,7 @@ static void builtin_diff(const char *name_a,
 		struct emit_callback ecbdata;
 		const struct userdiff_funcname *pe;
 
-		if (!DIFF_XDL_TST(o, WHITESPACE_FLAGS)) {
+		if (!DIFF_XDL_TST(o, WHITESPACE_FLAGS) || must_show_header) {
 			fprintf(o->file, "%s", header.buf);
 			strbuf_reset(&header);
 		}
@@ -2315,8 +2322,10 @@ static void fill_metainfo(struct strbuf *msg,
 			  struct diff_filespec *one,
 			  struct diff_filespec *two,
 			  struct diff_options *o,
-			  struct diff_filepair *p)
+			  struct diff_filepair *p,
+			  int *must_show_header)
 {
+	*must_show_header = 1;
 	strbuf_init(msg, PATH_MAX * 2 + 300);
 	switch (p->status) {
 	case DIFF_STATUS_COPIED:
@@ -2344,7 +2353,7 @@ static void fill_metainfo(struct strbuf *msg,
 		/* fallthru */
 	default:
 		/* nothing */
-		;
+		*must_show_header = 0;
 	}
 	if (one && two && hashcmp(one->sha1, two->sha1)) {
 		int abbrev = DIFF_OPT_TST(o, FULL_INDEX) ? 40 : DEFAULT_ABBREV;
@@ -2378,9 +2387,10 @@ static void run_diff_cmd(const char *pgm,
 {
 	const char *xfrm_msg = NULL;
 	int complete_rewrite = (p->status == DIFF_STATUS_MODIFIED) && p->score;
+	int must_show_header = 0;
 
 	if (msg) {
-		fill_metainfo(msg, name, other, one, two, o, p);
+		fill_metainfo(msg, name, other, one, two, o, p, &must_show_header);
 		xfrm_msg = msg->len ? msg->buf : NULL;
 	}
 
@@ -2399,7 +2409,8 @@ static void run_diff_cmd(const char *pgm,
 	}
 	if (one && two)
 		builtin_diff(name, other ? other : name,
-			     one, two, xfrm_msg, o, complete_rewrite);
+			     one, two, xfrm_msg, must_show_header,
+			     o, complete_rewrite);
 	else
 		fprintf(o->file, "* Unmerged path %s\n", name);
 }

t/t4015-diff-whitespace.sh

@@ -396,6 +396,43 @@ test_expect_success 'whitespace-only changes not reported' '
 	test_cmp expect actual
 '
 
+cat <<EOF >expect
+diff --git a/x b/z
+similarity index NUM%
+rename from x
+rename to z
+index 380c32a..a97b785 100644
+EOF
+test_expect_success 'whitespace-only changes reported across renames' '
+	git reset --hard &&
+	for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
+	git add x &&
+	git commit -m "base" &&
+	sed -e "5s/^/ /" x >z &&
+	git rm x &&
+	git add z &&
+	git diff -w -M --cached |
+	sed -e "/^similarity index /s/[0-9][0-9]*/NUM/" >actual &&
+	test_cmp expect actual
+'
+
+cat >expected <<\EOF
+diff --git a/empty b/void
+similarity index 100%
+rename from empty
+rename to void
+EOF
+
+test_expect_success 'rename empty' '
+	git reset --hard &&
+	>empty &&
+	git add empty &&
+	git commit -m empty &&
+	git mv empty void &&
+	git diff -w --cached -M >current &&
+	test_cmp expected current
+'
+
 test_expect_success 'combined diff with autocrlf conversion' '
 
 	git reset --hard &&

t/t4043-diff-rename-binary.sh

@@ -0,0 +1,45 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Jakub Narebski, Christian Couder
+#
+
+test_description='Move a binary file'
+
+. ./test-lib.sh
+
+
+test_expect_success 'prepare repository' '
+	git init &&
+	echo foo > foo &&
+	echo "barQ" | q_to_nul > bar &&
+	git add . &&
+	git commit -m "Initial commit"
+'
+
+test_expect_success 'move the files into a "sub" directory' '
+	mkdir sub &&
+	git mv bar foo sub/ &&
+	git commit -m "Moved to sub/"
+'
+
+cat > expected <<\EOF
+ bar => sub/bar |  Bin 5 -> 5 bytes
+ foo => sub/foo |    0
+ 2 files changed, 0 insertions(+), 0 deletions(-)
+
+diff --git a/bar b/sub/bar
+similarity index 100%
+rename from bar
+rename to sub/bar
+diff --git a/foo b/sub/foo
+similarity index 100%
+rename from foo
+rename to sub/foo
+EOF
+
+test_expect_success 'git show -C -C report renames' '
+	git show -C -C --raw --binary --stat | tail -n 12 > current &&
+	test_cmp expected current
+'
+
+test_done