In Spark 1.x releases we provided the CHANGES.txt file which proved useful to know exactly the differences and commit IDs between releases
In Spark 2.x we made packaging changes (moving make-distribution.sh to be under dev and different structure for the important Spark classes e.g. no big assembly jar), so I expect work wasn't done to ensure the changes file was still being provided
Note that users can view the release notes online (https://issues.apache.org/jira/secure/ReleaseNote.jspa?projectId=12315420&version=12336857) so I don't know if there is merit in including this file in the distribution, but I've had a look in the codebase and noticed the script used to generate said file is still present in master and definitely out of date:
https://github.com/apache/spark/blob/master/dev/create-release/generate-changelist.py, here we see the last commit is from the 27th of August 2014
If we change this to
we can create a CHANGES.txt.new file
So I think this file should be either be removed in 2.x. or updated across our currently maintained branches and then we'd need to run the make-distribution script to ensure the file is picked up and included in the distribution
I see no JIRAs mentioning "changes" under the spark project and no discussion of this on either mailing list. I downloaded the Spark 2.0.0 tgz (no 2.0.1 tgz at http://spark.apache.org/downloads.html) and verified there is no changes file here.