Preserve a log file's modification time on rotation

What steps will reproduce the problem?

Use Yii's FileTarget enough to cause log file rotation.

What is the expected result?

FS modification time of each log file indicates the date-time when that log file was last written.

What do you get instead?

It indicates when the file was last copied in a rotation.

It is likely enough to add one line to the FileTarget::rotateByCopy() function

        @touch($newFile, filemtime($rotateFile));