Bundle 64-bit pageant with 64-bit TortoiseHG
Pageant bundled with TortoiseHG 64-bit is 32-bit. It cannot recognise "user@" part in an URL, and keeps asking for user name. Replacing it with a 64-bit version fixes this issue. It's required for pushing using hg-git for example.
Use 64-bit Pageant from here, or compile one from sources: https://splunk.net/w/PuTTy64bit