Fix some small Diffusion file browse view bugs

Summary:
"--date short" was introduced to git somewhere between 1.7.2.2 and 1.7.3.4,
despite 1.7.2.2 saying "--date <format>" in "git help blame". The older version
of git accepts "--date=short", however.

Also, the URI construction means you get "?view=" if you click a line number to
get a deep link, which I found vaguely annoying. Drop 'view' if we don't need
it.

Test Plan:
Looked at blame in my sandbox, although it worked before the date patch since I
have 1.7.3.4. Clicked a line number. Switched viewmodes.

Reviewed By: codeblock
Reviewers: codeblock, jungejason, tuomaspelkonen, aran
CC: aran, codeblock
Differential Revision: 423