ceki/logback — comment on commit c0d9b3b41b6cac04daa19d30f7a262ba81e8e319
File: logback-core/src/main/java/ch/qos/logback/core/rolling/SizeAndTimeBasedFNATP.java line 65
By trothwell:

If current compression != NONE, then stemRegex included compression suffix.
If current compression == NONE, then stemRegex did not include compression suffix.
Care should be taken if the user changed the compression value as the highestCounter wouldn't notice the compressed or uncompressed files.