R1:a546b029b0bc

Censor credentials possibly present in Git remote URIs when pulls fail because of a URI mismatch

Summary: Fixes T12945.

Test Plan:
Mostly faked this, got a censored error:

```
$ ./bin/repository update R38
[2017-07-31 19:40:13] EXCEPTION: (Exception) Working copy at "/Users/epriestley/dev/core/repo/local/38/" has a mismatched origin URI, "https://********@example.com/". The expected origin URI is "https://github.com/phacility/libphutil.git". Fix your configuration, or set the remote URI correctly. To…