Commits are truly atomic

Atomic commits are basic to transaction processing. If you go to an ATM machine and transfer money from account A to account B you want to make sure that either (a) the transfer did occur completely or (b) the transfer failed completely. There are two other ``non-atomic'' options (c) the bank deducted the transfer from account A and did not credit account B (thus you lost money) or (d) the bank credited account B but never debited account A (thus you gained money).

If you make a set of changes to many files you either want them all to appear or none of them to appear. Since CVS does each file change individually it is possible to get only parts of changes committed. GNU-Arch has the concept of a ``changeset'' which means that instead of viewing a commit as a series of changes to individual files you group the changes together.