Merge branch 'jc/apply-ignore-whitespace' into maint

"--ignore-space-change" option of "git apply" ignored the spaces
at the beginning of line too aggressively, which is inconsistent
with the option of the same name "diff" and "git diff" have.

* jc/apply-ignore-whitespace:
  apply --ignore-space-change: lines with and without leading whitespaces do not match

builtin/apply.c

@@ -300,11 +300,13 @@ static int fuzzy_matchlines(const char *s1, size_t n1,
 	while ((*last2 == '\r') || (*last2 == '\n'))
 		last2--;
 
-	/* skip leading whitespace */
-	while (isspace(*s1) && (s1 <= last1))
-		s1++;
-	while (isspace(*s2) && (s2 <= last2))
-		s2++;
+	/* skip leading whitespaces, if both begin with whitespace */
+	if (s1 <= last1 && s2 <= last2 && isspace(*s1) && isspace(*s2)) {
+		while (isspace(*s1) && (s1 <= last1))
+			s1++;
+		while (isspace(*s2) && (s2 <= last2))
+			s2++;
+	}
 	/* early return if both lines are empty */
 	if ((s1 > last1) && (s2 > last2))
 		return 1;

t/t4107-apply-ignore-whitespace.sh

@@ -111,7 +111,6 @@ sed -e 's/T/	/g' > main.c.final <<\EOF
 #include <stdio.h>
 
 void print_int(int num);
-T/* a comment */
 int func(int num);
 
 int main() {
@@ -154,7 +153,8 @@ test_expect_success 'patch2 reverse applies with --ignore-space-change' '
 git config apply.ignorewhitespace change
 
 test_expect_success 'patch2 applies (apply.ignorewhitespace = change)' '
-	git apply patch2.patch
+	git apply patch2.patch &&
+	test_cmp main.c.final main.c
 '
 
 test_expect_success 'patch3 fails (missing string at EOL)' '
@@ -165,12 +165,8 @@ test_expect_success 'patch4 fails (missing EOL at EOF)' '
 	test_must_fail git apply patch4.patch
 '
 
-test_expect_success 'patch5 applies (leading whitespace)' '
-	git apply patch5.patch
-'
-
-test_expect_success 'patches do not mangle whitespace' '
-	test_cmp main.c main.c.final
+test_expect_success 'patch5 fails (leading whitespace differences matter)' '
+	test_must_fail git apply patch5.patch
 '
 
 test_expect_success 're-create file (with --ignore-whitespace)' '