Fix ExecCommandWith for cmd.exe in Windows (#1072)

Close #1018

Run the command as is in cmd.exe with no parsing and escaping.
Explicity set cmd.SysProcAttr so execCommand does not escape the command.
Technically, the command should be escaped with ^ for special characters,
including ". This allows cmd.exe commands to be chained together.

See https://github.com/neovim/neovim/pull/7343#issuecomment-333350201

This commit also updates quoteEntry to use strings.Replace instead of
strconv.Quote which escapes more than \ and ".

src/terminal_test.go

@@ -91,3 +91,22 @@ func TestReplacePlaceholder(t *testing.T) {
 	result = replacePlaceholder("echo {}/{1}/{3}/{2..3}", true, Delimiter{regex: regex}, false, "query", items1)
 	check("echo '  foo'\\''bar baz'/'f'/'r b'/''\\''bar b'")
 }
+
+func TestQuoteEntryCmd(t *testing.T) {
+	tests := map[string]string{
+		`"`:                       `^"\^"^"`,
+		`\`:                       `^"\\^"`,
+		`\"`:                      `^"\\\^"^"`,
+		`"\\\"`:                   `^"\^"\\\\\\\^"^"`,
+		`&|<>()@^%!`:              `^"^&^|^<^>^(^)^@^^^%^!^"`,
+		`%USERPROFILE%`:           `^"^%USERPROFILE^%^"`,
+		`C:\Program Files (x86)\`: `^"C:\\Program Files ^(x86^)\\^"`,
+	}
+
+	for input, expected := range tests {
+		escaped := quoteEntryCmd(input)
+		if escaped != expected {
+			t.Errorf("Input: %s, expected: %s, actual %s", input, expected, escaped)
+		}
+	}
+}