This addresses issue #2621
This commit turns out to be a partial revert of
ea3c01e3374143912f048b22fda106ee8d5a1cd8
The rationale is that a `|` character preceding a match pattern is not
semantically relevant and therefore should be considered a
style/formatting choice.
A discussion concluded that the best way to emit consistent formatting
here was to strip the leading `|`
This removes the match_with_beginning_vert test because it was asserting
the old behaviour which has been changed, it adds a new test
(issue_2621) which should be a more comprehensive check of the behavior
of `|` in match arms.
Discussion at https://github.com/rust-lang-nursery/fmt-rfcs/issues/119
1d4b988414