[patch|minor|major]? auto syntax has some possible hidden traps

[tyler-jachetta]

Due to how the regex is constructed when finding the bump to perform, e.g. "[patches applied to the..." and "[minor changes only]" will both result in an auto bump.

I think it makes sense to only accept [<bump type> when there is a closing bracket immediately aftewrwards (perhaps with whitespace allowed inside, similar to what I did in #61).