Maintain backward compatibiliy withour onConnect callback.

In f69fac7690fb22a7fc19dba61ef70e5f79ccb2e9, our async onConnect
callback was improved to take a non-const redisAsyncContext allowing it
to be reentrant.

Unfortunately, this is a breaking change we can't make until hiredis
v2.0.0.

This commit creates a separate callback member and corresponding
function that allows us to use the new functionality, while maintaining
our existing API for legacy code.

Fixes #1086

1 files changed, 2 insertions, 0 deletions

diff --git a/README.md b/README.md
index b0b2aff..ff50d13 100644
--- a/README.md
+++ b/README.md
@@ -372,6 +372,8 @@ the disconnect callback is a good point to do so.
 Setting the connect or disconnect callbacks can only be done once per context. For subsequent calls the
 api will return `REDIS_ERR`. The function to set the callbacks have the following prototype:
 ```c
+/* Alternatively you can use redisAsyncSetConnectCallbackNC which will be passed a non-const
+   redisAsyncContext* on invocation (e.g. allowing writes to the privdata member). */
 int redisAsyncSetConnectCallback(redisAsyncContext *ac, redisConnectCallback *fn);
 int redisAsyncSetDisconnectCallback(redisAsyncContext *ac, redisDisconnectCallback *fn);
 ```