remote-curl: make --force-with-lease work with non-ASCII ref names

When we invoke a remote transport helper and pass an option with an
argument, we quote the argument as a C-style string if necessary.  This
is the case for the cas option, which implements the --force-with-lease
command-line flag, when we're passing a non-ASCII refname.

However, the remote curl helper isn't designed to parse such an
argument, meaning that if we try to use --force-with-lease with an HTTP
push and a non-ASCII refname, we get an error like this:

  error: cannot parse expected object name '0000000000000000000000000000000000000000"'

Note the double quote, which get_oid has reminded us is not valid in an
hex object ID.

Even if we had been able to parse it, we would send the wrong data to
the server: we'd send an escaped ref, which would not behave as the user
wanted and might accidentally result in updating or deleting a ref we
hadn't intended.

Since we need to expect a quoted C-style string here, just check if the
first argument is a double quote, and if so, unquote it.  Note that if
the refname contains a double quote, then we will have double-quoted it
already, so there is no ambiguity.

We test for this case only in the smart protocol, since the DAV-based
protocol is not capable of handling this capability.  We use UTF-8
because this is nicer in our tests and friendlier to Windows, but the
code should work for all non-ASCII refs.

While we're at it, since the name of the option is now well established
and isn't going to change, let's inline it instead of using the #define
constant.

Reported-by: Frej Bjon <frej.bjon@nemit.fi>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

remote-curl.c

@@ -119,7 +119,11 @@ static int set_option(const char *name, const char *value)
 	}
 	else if (!strcmp(name, "cas")) {
 		struct strbuf val = STRBUF_INIT;
-		strbuf_addf(&val, "--" CAS_OPT_NAME "=%s", value);
+		strbuf_addstr(&val, "--force-with-lease=");
+		if (*value != '"')
+			strbuf_addstr(&val, value);
+		else if (unquote_c_style(&val, value, NULL))
+			return -1;
 		string_list_append(&cas_options, val.buf);
 		strbuf_release(&val);
 		return 0;