Merge branch 'jc/checkdiff'

* jc/checkdiff:
  Fix t4017-diff-retval for white-space from wc
  Update sample pre-commit hook to use "diff --check"
  diff --check: detect leftover conflict markers
  Teach "diff --check" about new blank lines at end
  checkdiff: pass diff_options to the callback
  check_and_emit_line(): rename and refactor
  diff --check: explain why we do not care whether old side is binary

7 files changed, 136 insertions, 87 deletions

diff --git a/builtin-apply.c b/builtin-apply.c
index 318504a03..985ca3be5 100644
--- a/builtin-apply.c
+++ b/builtin-apply.c
@@ -987,8 +987,7 @@ static int find_header(char *line, unsigned long size, int *hdrsize, struct patc
 static void check_whitespace(const char *line, int len, unsigned ws_rule)
 {
 	char *err;
-	unsigned result = check_and_emit_line(line + 1, len - 1, ws_rule,
-	    NULL, NULL, NULL, NULL);
+	unsigned result = ws_check(line + 1, len - 1, ws_rule);
 	if (!result)
 		return;
 
@@ -999,7 +998,7 @@ static void check_whitespace(const char *line, int len, unsigned ws_rule)
 	else {
 		err = whitespace_error_string(result);
 		fprintf(stderr, "%s:%d: %s.\n%.*s\n",
-		     patch_input_file, linenr, err, len - 2, line + 1);
+			patch_input_file, linenr, err, len - 2, line + 1);
 		free(err);
 	}
 }
diff --git a/cache.h b/cache.h
index 64ef86e12..188428dd2 100644
--- a/cache.h
+++ b/cache.h
@@ -819,11 +819,11 @@ void shift_tree(const unsigned char *, const unsigned char *, unsigned char *, i
 extern unsigned whitespace_rule_cfg;
 extern unsigned whitespace_rule(const char *);
 extern unsigned parse_whitespace_rule(const char *);
-extern unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
-    FILE *stream, const char *set,
-    const char *reset, const char *ws);
+extern unsigned ws_check(const char *line, int len, unsigned ws_rule);
+extern void ws_check_emit(const char *line, int len, unsigned ws_rule, FILE *stream, const char *set, const char *reset, const char *ws);
 extern char *whitespace_error_string(unsigned ws);
 extern int ws_fix_copy(char *, const char *, int, unsigned, int *);
+extern int ws_blank_line(const char *line, int len, unsigned ws_rule);
 
 /* ls-files */
 int pathspec_match(const char **spec, char *matched, const char *filename, int skiplen);
diff --git a/diff.c b/diff.c
index 66851b564..803fbba45 100644
--- a/diff.c
+++ b/diff.c
@@ -535,9 +535,9 @@ static void emit_add_line(const char *reset, struct emit_callback *ecbdata, cons
 	else {
 		/* Emit just the prefix, then the rest. */
 		emit_line(ecbdata->file, set, reset, line, ecbdata->nparents);
-		(void)check_and_emit_line(line + ecbdata->nparents,
-		    len - ecbdata->nparents, ecbdata->ws_rule,
-		    ecbdata->file, set, reset, ws);
+		ws_check_emit(line + ecbdata->nparents,
+			      len - ecbdata->nparents, ecbdata->ws_rule,
+			      ecbdata->file, set, reset, ws);
 	}
 }
 
@@ -1136,42 +1136,85 @@ static void free_diffstat_info(struct diffstat_t *diffstat)
 struct checkdiff_t {
 	struct xdiff_emit_state xm;
 	const char *filename;
-	int lineno, color_diff;
+	int lineno;
+	struct diff_options *o;
 	unsigned ws_rule;
 	unsigned status;
-	FILE *file;
+	int trailing_blanks_start;
 };
 
+static int is_conflict_marker(const char *line, unsigned long len)
+{
+	char firstchar;
+	int cnt;
+
+	if (len < 8)
+		return 0;
+	firstchar = line[0];
+	switch (firstchar) {
+	case '=': case '>': case '<':
+		break;
+	default:
+		return 0;
+	}
+	for (cnt = 1; cnt < 7; cnt++)
+		if (line[cnt] != firstchar)
+			return 0;
+	/* line[0] thru line[6] are same as firstchar */
+	if (firstchar == '=') {
+		/* divider between ours and theirs? */
+		if (len != 8 || line[7] != '\n')
+			return 0;
+	} else if (len < 8 || !isspace(line[7])) {
+		/* not divider before ours nor after theirs */
+		return 0;
+	}
+	return 1;
+}
+
 static void checkdiff_consume(void *priv, char *line, unsigned long len)
 {
 	struct checkdiff_t *data = priv;
-	const char *ws = diff_get_color(data->color_diff, DIFF_WHITESPACE);
-	const char *reset = diff_get_color(data->color_diff, DIFF_RESET);
-	const char *set = diff_get_color(data->color_diff, DIFF_FILE_NEW);
+	int color_diff = DIFF_OPT_TST(data->o, COLOR_DIFF);
+	const char *ws = diff_get_color(color_diff, DIFF_WHITESPACE);
+	const char *reset = diff_get_color(color_diff, DIFF_RESET);
+	const char *set = diff_get_color(color_diff, DIFF_FILE_NEW);
 	char *err;
 
 	if (line[0] == '+') {
 		unsigned bad;
 		data->lineno++;
-		bad = check_and_emit_line(line + 1, len - 1,
-		    data->ws_rule, NULL, NULL, NULL, NULL);
+		if (!ws_blank_line(line + 1, len - 1, data->ws_rule))
+			data->trailing_blanks_start = 0;
+		else if (!data->trailing_blanks_start)
+			data->trailing_blanks_start = data->lineno;
+		if (is_conflict_marker(line + 1, len - 1)) {
+			data->status |= 1;
+			fprintf(data->o->file,
+				"%s:%d: leftover conflict marker\n",
+				data->filename, data->lineno);
+		}
+		bad = ws_check(line + 1, len - 1, data->ws_rule);
 		if (!bad)
 			return;
 		data->status |= bad;
 		err = whitespace_error_string(bad);
-		fprintf(data->file, "%s:%d: %s.\n", data->filename, data->lineno, err);
+		fprintf(data->o->file, "%s:%d: %s.\n",
+			data->filename, data->lineno, err);
 		free(err);
-		emit_line(data->file, set, reset, line, 1);
-		(void)check_and_emit_line(line + 1, len - 1, data->ws_rule,
-		    data->file, set, reset, ws);
-	} else if (line[0] == ' ')
+		emit_line(data->o->file, set, reset, line, 1);
+		ws_check_emit(line + 1, len - 1, data->ws_rule,
+			      data->o->file, set, reset, ws);
+	} else if (line[0] == ' ') {
 		data->lineno++;
-	else if (line[0] == '@') {
+		data->trailing_blanks_start = 0;
+	} else if (line[0] == '@') {
 		char *plus = strchr(line, '+');
 		if (plus)
 			data->lineno = strtol(plus, NULL, 10) - 1;
 		else
 			die("invalid diff");
+		data->trailing_blanks_start = 0;
 	}
 }
 
@@ -1544,8 +1587,9 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 
 static void builtin_checkdiff(const char *name_a, const char *name_b,
 			      const char *attr_path,
-			     struct diff_filespec *one,
-			     struct diff_filespec *two, struct diff_options *o)
+			      struct diff_filespec *one,
+			      struct diff_filespec *two,
+			      struct diff_options *o)
 {
 	mmfile_t mf1, mf2;
 	struct checkdiff_t data;
@@ -1557,13 +1601,18 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 	data.xm.consume = checkdiff_consume;
 	data.filename = name_b ? name_b : name_a;
 	data.lineno = 0;
-	data.color_diff = DIFF_OPT_TST(o, COLOR_DIFF);
+	data.o = o;
 	data.ws_rule = whitespace_rule(attr_path);
-	data.file = o->file;
 
 	if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
 		die("unable to read files to diff");
 
+	/*
+	 * All the other codepaths check both sides, but not checking
+	 * the "old" side here is deliberate.  We are checking the newly
+	 * introduced changes, and as long as the "new" side is text, we
+	 * can and should check what it introduces.
+	 */
 	if (diff_filespec_is_binary(two))
 		goto free_and_return;
 	else {
@@ -1577,6 +1626,12 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 		ecb.outf = xdiff_outf;
 		ecb.priv = &data;
 		xdi_diff(&mf1, &mf2, &xpp, &xecfg, &ecb);
+
+		if (data.trailing_blanks_start) {
+			fprintf(o->file, "%s:%d: ends with blank lines.\n",
+				data.filename, data.trailing_blanks_start);
+			data.status = 1; /* report errors */
+		}
 	}
  free_and_return:
 	diff_free_filespec_data(one);
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index b7cc6b28e..0922c708f 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -335,4 +335,10 @@ test_expect_success 'line numbers in --check output are correct' '
 
 '
 
+test_expect_success 'checkdiff detects trailing blank lines' '
+	echo "foo();" >x &&
+	echo "" >>x &&
+	git diff --check | grep "ends with blank"
+'
+
 test_done
diff --git a/t/t4017-diff-retval.sh b/t/t4017-diff-retval.sh
index 0d0fb87f5..60dd2014d 100755
--- a/t/t4017-diff-retval.sh
+++ b/t/t4017-diff-retval.sh
@@ -113,4 +113,18 @@ test_expect_success 'check should test not just the last line' '
 
 '
 
+test_expect_success 'check detects leftover conflict markers' '
+	git reset --hard &&
+	git checkout HEAD^ &&
+	echo binary >>b &&
+	git commit -m "side" b &&
+	test_must_fail git merge master &&
+	git add b && (
+		git --no-pager diff --cached --check >test.out
+		test $? = 2
+	) &&
+	test 3 = $(grep "conflict marker" test.out | wc -l) &&
+	git reset --hard
+'
+
 test_done
diff --git a/templates/hooks--pre-commit.sample b/templates/hooks--pre-commit.sample
index 71c10f25f..0e49279c7 100755
--- a/templates/hooks--pre-commit.sample
+++ b/templates/hooks--pre-commit.sample
@@ -7,64 +7,12 @@
 #
 # To enable this hook, rename this file to "pre-commit".
 
-# This is slightly modified from Andrew Morton's Perfect Patch.
-# Lines you introduce should not have trailing whitespace.
-# Also check for an indentation that has SP before a TAB.
-
 if git-rev-parse --verify HEAD 2>/dev/null
 then
-	git-diff-index -p -M --cached HEAD --
+	against=HEAD
 else
-	# NEEDSWORK: we should produce a diff with an empty tree here
-	# if we want to do the same verification for the initial import.
-	:
-fi |
-perl -e '
-    my $found_bad = 0;
-    my $filename;
-    my $reported_filename = "";
-    my $lineno;
-    sub bad_line {
-	my ($why, $line) = @_;
-	if (!$found_bad) {
-	    print STDERR "*\n";
-	    print STDERR "* You have some suspicious patch lines:\n";
-	    print STDERR "*\n";
-	    $found_bad = 1;
-	}
-	if ($reported_filename ne $filename) {
-	    print STDERR "* In $filename\n";
-	    $reported_filename = $filename;
-	}
-	print STDERR "* $why (line $lineno)\n";
-	print STDERR "$filename:$lineno:$line\n";
-    }
-    while (<>) {
-	if (m|^diff --git a/(.*) b/\1$|) {
-	    $filename = $1;
-	    next;
-	}
-	if (/^@@ -\S+ \+(\d+)/) {
-	    $lineno = $1 - 1;
-	    next;
-	}
-	if (/^ /) {
-	    $lineno++;
-	    next;
-	}
-	if (s/^\+//) {
-	    $lineno++;
-	    chomp;
-	    if (/\s$/) {
-		bad_line("trailing whitespace", $_);
-	    }
-	    if (/^\s* \t/) {
-		bad_line("indent SP followed by a TAB", $_);
-	    }
-	    if (/^([<>])\1{6} |^={7}$/) {
-		bad_line("unresolved merge conflict", $_);
-	    }
-	}
-    }
-    exit($found_bad);
-'
+	# Initial commit: diff against an empty tree object
+	against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+fi
+
+exec git diff-index --check --cached $against --
diff --git a/ws.c b/ws.c
index ba7e834ca..7a7ff130a 100644
--- a/ws.c
+++ b/ws.c
@@ -117,9 +117,9 @@ char *whitespace_error_string(unsigned ws)
 }
 
 /* If stream is non-NULL, emits the line after checking. */
-unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
-			     FILE *stream, const char *set,
-			     const char *reset, const char *ws)
+static unsigned ws_check_emit_1(const char *line, int len, unsigned ws_rule,
+				FILE *stream, const char *set,
+				const char *reset, const char *ws)
 {
 	unsigned result = 0;
 	int written = 0;
@@ -213,6 +213,33 @@ unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
 	return result;
 }
 
+void ws_check_emit(const char *line, int len, unsigned ws_rule,
+		   FILE *stream, const char *set,
+		   const char *reset, const char *ws)
+{
+	(void)ws_check_emit_1(line, len, ws_rule, stream, set, reset, ws);
+}
+
+unsigned ws_check(const char *line, int len, unsigned ws_rule)
+{
+	return ws_check_emit_1(line, len, ws_rule, NULL, NULL, NULL, NULL);
+}
+
+int ws_blank_line(const char *line, int len, unsigned ws_rule)
+{
+	/*
+	 * We _might_ want to treat CR differently from other
+	 * whitespace characters when ws_rule has WS_CR_AT_EOL, but
+	 * for now we just use this stupid definition.
+	 */
+	while (len-- > 0) {
+		if (!isspace(*line))
+			return 0;
+		line++;
+	}
+	return 1;
+}
+
 /* Copy the line to the buffer while fixing whitespaces */
 int ws_fix_copy(char *dst, const char *src, int len, unsigned ws_rule, int *error_count)
 {