In the case of email, it can be argued that the widespread use of the unhyphenated spelling has made this compound noun an exception to the rule. It might also be said that closed (unhyphenated) spelling is simply the direction English is evolving, but good luck arguing that “tshirt” is a good way to write “t-shirt.”

“Have you brought your time sheet up to date yet?”

The use ofhyphens in compound words is becoming less frequent exceptwhen essential for clarity of meaning. The customary prac-tice is to write such words as coordinate with the dieresisrather than the hyphen.

Either, plus presumably "bug-fix." The word has almost surely been coined multiple times by people who hadn't heard it before, because the utility is obvious. In some universe where English was required to always make sense, the one-word or hyphenated forms would be the most likely, since two words implies that "bug" is an adjective.