Slowlog: don't log EXEC but just the executed commands.

The Redis Slow Log always used to log the slow commands executed inside
a MULTI/EXEC block. However also EXEC was logged at the end, which is
perfectly useless.

Now EXEC is no longer logged and a test was added to test this behavior.

This fixes issue #759.

src/redis.c

@@ -1511,7 +1511,7 @@ void call(redisClient *c, int flags) {
 
     /* Log the command into the Slow log if needed, and populate the
      * per-command statistics that we show in INFO commandstats. */
-    if (flags & REDIS_CALL_SLOWLOG)
+    if (flags & REDIS_CALL_SLOWLOG && c->cmd->proc != execCommand)
         slowlogPushEntryIfNeeded(c->argv,c->argc,duration);
     if (flags & REDIS_CALL_STATS) {
         c->cmd->microseconds += duration;

tests/unit/slowlog.tcl

@@ -55,4 +55,16 @@ start_server {tags {"slowlog"} overrides {slowlog-log-slower-than 1000000}} {
         set e [lindex [r slowlog get] 0]
         lindex $e 3
     } {sadd set foo {AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA... (1 more bytes)}}
+
+    test {SLOWLOG - EXEC is not logged, just executed commands} {
+        r config set slowlog-log-slower-than 100000
+        r slowlog reset
+        assert_equal [r slowlog len] 0
+        r multi
+        r debug sleep 0.2
+        r exec
+        assert_equal [r slowlog len] 1
+        set e [lindex [r slowlog get] 0]
+        assert_equal [lindex $e 3] {debug sleep 0.2}
+    }
 }