CCBC-350: Add cntl to report changeset used by binary

Change-Id: Ib8240c4d899fdf3f6c4988a52f23ddf2e37def8b
Reviewed-on: http://review.couchbase.org/34898
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>

include/libcouchbase/cntl.h

@@ -433,8 +433,15 @@ extern "C" {
      */
 #define LCB_CNTL_CONFIG_CCCP_NODES 0x1E
 
+    /**
+     * Get the current SCM changeset for the library binary
+     * Arg: char** to contain the resultant string. This string must not be
+     * freed
+     */
+#define LCB_CNTL_CHANGESET 0x1F
+
     /** This is not a command, but rather an indicator of the last item */
-#define LCB_CNTL__MAX                    0x1F
+#define LCB_CNTL__MAX                    0x20
 
 
 #ifdef __cplusplus

src/cntl.c

@@ -447,6 +447,15 @@ static lcb_error_t config_nodes(int mode, lcb_t instance, int cmd, void *arg)
     return LCB_SUCCESS;
 }
 
+static lcb_error_t get_changeset(int mode, lcb_t instance, int cmd, void *arg)
+{
+    *(char **)arg = LCB_VERSION_CHANGESET;
+    (void)instance;
+    (void)mode;
+    (void)cmd;
+    return LCB_SUCCESS;
+}
+
 static ctl_handler handlers[] = {
     timeout_common, /* LCB_CNTL_OP_TIMEOUT */
     timeout_common, /* LCB_CNTL_VIEW_TIMEOUT */
@@ -478,7 +487,8 @@ static ctl_handler handlers[] = {
     timeout_common, /* LCB_CNTL_CONFIG_NODE_TIMEOUT */
     timeout_common, /* LCB_CNTL_HTCONFIG_IDLE_TIMEOUT */
     config_nodes, /* LCB_CNTL_CONFIG_HTTP_NODES */
-    config_nodes /* LCB_CNTL_CONFIG_CCCP_NODES */
+    config_nodes, /* LCB_CNTL_CONFIG_CCCP_NODES */
+    get_changeset /* LCB_CNTL_CHANGESET */
 };