In the last days I've experienced very slow connections when pushing new commits to Bitbucket via shell or via SourceTree. The push of a commit with just one file changed took about 60 seconds or even more. After googling around without finding any helpful answers, I lived with the problem for some days. Today I decided to debug the ssh connection while pushing (why didn't I do that first ...).
ssh -Tv email@example.com [...] debug1: Connecting to bitbucket.org [2401:1d80:1010::152] port 22. debug1: connect to address 2401:1d80:1010::152 port 22: Operation timed out debug1: Connecting to bitbucket.org [220.127.116.11] port 22. debug1: Connection established. [...]
It turned out that the SSH connection via IPV6 had a timeout and afterwards IPV4 is used. This happend with every commit. As a quick fix, I decided to turn off IPV6 for SSH and added
[...] AddressFamily inet # IPv4 only [...]
/etc/ssh/sshd_config file. Afterwards I restarted my OSX to completely have sshd restarted and everything worked just fine again.