Merge branch 'rs/grep-parser-fix'

"git grep --and -e foo" ought to have been diagnosed as an error
but instead segfaulted, which has been corrected.

* rs/grep-parser-fix:
  grep: report missing left operand of --and

grep.c

@@ -657,6 +657,8 @@ static struct grep_expr *compile_pattern_and(struct grep_pat **list)
 	x = compile_pattern_not(list);
 	p = *list;
 	if (p && p->token == GREP_AND) {
+		if (!x)
+			die("--and not preceded by pattern expression");
 		if (!p->next)
 			die("--and not followed by pattern expression");
 		*list = p->next;

t/t7810-grep.sh

@@ -11,6 +11,13 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
 
+test_invalid_grep_expression() {
+	params="$@" &&
+	test_expect_success "invalid expression: grep $params" '
+		test_must_fail git grep $params -- nonexisting
+	'
+}
+
 cat >hello.c <<EOF
 #include <assert.h>
 #include <stdio.h>
@@ -89,6 +96,8 @@ test_expect_success 'grep should not segfault with a bad input' '
 	test_must_fail git grep "("
 '
 
+test_invalid_grep_expression --and -e A
+
 for H in HEAD ''
 do
 	case "$H" in