R1:8f772929ac61

Use a password input for HTTP Basic Auth in repositories

Summary: See D902. As @abdul notes, a password input is probably more
appropraite here.

Test Plan: Mashed stuff into it, got bullets instead of text.

Reviewers: abdul, jungejason, nh, tuomaspelkonen, aran

Reviewed By: nh

CC: aran, nh

Differential Revision: 913