if i were to take a guess, the programmer first typed out all the if conditional expressions, then went in and pasted 'goto fail' out of a buffer after each one, and accidentally did it twice there.
plese use some imagination before jumping to conclusions. a diff tracks changes at points in time, not an editing session.
he could have easily yanked a goto line 'yy' for use elsewhere or by accident and pasted it by accident with 'p' right after he yanked it.
i see two very similar lines, 49 and 53, which were probably copy/pasted and edited. it is completely reasonable to assume he accidentally did it with another line further down the file.
he could have refactored this code multiple times before re-committing this file, moving blocks around or editing lines. there's plenty of opportunity to introduce errors.
do you understand how editing works?
if the entire diff was just + goto fail; that would be extremely suspicious, but that doesn't seem to be the case.