Improve dbid range check for SELECT, MOVE, COPY (#8085)

SELECT used to read the index into a `long` variable, and then pass it to a function
that takes an `int`, possibly causing an overflow before the range check.

Now all these commands use better and cleaner range check, and that also results in
a slight change of the error response in case of an invalid database index.

SELECT:
in the past it would have returned either `-ERR invalid DB index` (if not a number),
or `-ERR DB index is out of range` (if not between 1..16 or alike).
now it'll return either `-ERR value is out of range` (if not a number), or
`-ERR value is out of range, value must between -2147483648 and 2147483647`
(if not in the range for an int), or `-ERR DB index is out of range`
(if not between 0..16 or alike)


MOVE:
in the past it would only fail with `-ERR index out of range` no matter the reason.
now return the same errors as the new ones for SELECT mentioned above.
(i.e. unlike for SELECT even for a value like 17 we changed the error message)

COPY:
doesn't really matter how it behaved in the past (new command), new behavior is
like the above two.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/object.c b/src/object.c
index d35ba0eaf..71eceb6d6 100644
--- a/src/object.c
+++ b/src/object.c
@@ -747,6 +747,16 @@ int getPositiveLongFromObjectOrReply(client *c, robj *o, long *target, const cha
     return getRangeLongFromObjectOrReply(c, o, 0, LONG_MAX, target, msg);
 }
 
+int getIntFromObjectOrReply(client *c, robj *o, int *target, const char *msg) {
+    long value;
+
+    if (getRangeLongFromObjectOrReply(c, o, INT_MIN, INT_MAX, &value, msg) != C_OK)
+        return C_ERR;
+
+    *target = value;
+    return C_OK;
+}
+
 char *strEncoding(int encoding) {
     switch(encoding) {
     case OBJ_ENCODING_RAW: return "raw";