credential_approve timeouts with latest git

[jeroen]

With recent git versions on Linux and Windows we see a timeout (maybe due to user prompt)

> ### Name: credential_api
> ### Title: Retrieve and store git HTTPS credentials
> ### Aliases: credential_api credential_fill credential_approve
> ###   credential_reject
> 
> ### ** Examples
> 
> ## No test: 
> # Insert example cred
> example <- list(protocol = "https", host = "example.org",
+   username = "test", password = "secret")
> credential_approve(example)
Error: Error: Program 'git' terminated (timeout reached: 10.00sec)