meta: fix ms c flag reflecting s flag

Fixes memcached#1045

The parser for allowing metaset to return flags is a bad hack requiring
re-writing flags into a buffer then re-parsing them later. The newer
proxy parser doesn't need to do this and is thus safer from these
non-obvious bugs.

Added basic test coverage as well. It looks like ms with c was never
explicitly tested before, so the existing tests didn't fail during
development.

Thanks to @zenbones for the report.

proto_text.c

@@ -1461,6 +1461,7 @@ static void process_mset_command(conn *c, token_t *tokens, const size_t ntokens)
             case 'c':
                 // need to set the cas value post-assignment.
                 META_CHAR(p, 'c');
+                break;
             case 's':
                 // get the final size post-fill
                 META_CHAR(p, 's');

t/metaget.t

@@ -156,7 +156,29 @@ my $sock = $server->sock;
 }
 
 {
-    diag "basic mset CAS";
+    note "ensure mset flag reflection doesn't bleed";
+    # mset return flags are internally implemented by stashing the flags in
+    # the write buffer then re-parsing them later (to preserve order...) so we
+    # need to check extra that I'm not being a dingus and forgetting a break
+    # statement.
+    print $sock "ms a 1\r\n1\r\n";
+    is(scalar <$sock>, "HD\r\n", "no flags");
+
+    print $sock "ms a 1 c\r\n1\r\n";
+    like(scalar <$sock>, qr/^HD c\d+\r\n/, "c flag");
+
+    print $sock "ms a 1 Otest\r\n1\r\n";
+    like(scalar <$sock>, qr/^HD Otest\r\n/, "O flag");
+
+    print $sock "ms a 1 s\r\n1\r\n";
+    like(scalar <$sock>, qr/^HD s1\r\n/, "s flag");
+
+    print $sock "ms a 1 k\r\n1\r\n";
+    like(scalar <$sock>, qr/^HD ka\r\n/, "k flag");
+}
+
+{
+    note "basic mset CAS";
     my $key = "msetcas";
     print $sock "ms $key 2\r\nbo\r\n";
     like(scalar <$sock>, qr/^HD/, "set test key");
@@ -174,7 +196,7 @@ my $sock = $server->sock;
 }
 
 {
-    diag "mdelete with cas";
+    note "mdelete with cas";
     my $key = "mdeltest";
     print $sock "ms $key 2\r\nzo\r\n";
     like(scalar <$sock>, qr/^HD/, "set test key");
@@ -191,7 +213,7 @@ my $sock = $server->sock;
 }
 
 {
-    diag "encoded binary keys";
+    note "encoded binary keys";
     # 44OG44K544OI is "tesuto" in katakana
     my $tesuto = "44OG44K544OI";
     print $sock "ms $tesuto 2 b\r\npo\r\n";
@@ -208,7 +230,7 @@ my $sock = $server->sock;
 }
 
 {
-    diag "marithmetic tests";
+    note "marithmetic tests";
     print $sock "ma mo\r\n";
     like(scalar <$sock>, qr/^NF\r/, "incr miss");
 
@@ -276,7 +298,7 @@ my $sock = $server->sock;
 # mset tests with mode switch flag (M)
 
 {
-    diag "mset mode switch";
+    note "mset mode switch";
     print $sock "ms modedefault 2 T120\r\naa\r\n";
     like(scalar <$sock>, qr/^HD/, "default set mode");
     mget_is({ sock => $sock,