convert: don't use long list comprehensions We are iterating over p4changes. Make the continue condition more clear and easier to add new conditions in future patches, by removing the list comprehension and move the condition into the existing for-loop.

changelog: keep track of file end in appender (issue5444) Previously, changelog.appender.end() would compute the end of the file by joining all the current appended data and checking the length. This is an O(n) operation. e240e914d226 introduced a seek call before every revlog write, which means we are hitting this O(n) behavior n times, which causes changelog writes during a pull to be n^2. In our large repo, this caused pulling 100k commits to go from 17s to 130s. With this fix, it's back to 17s.