Dockerfiles reference old Tomcat tag

[whikloj]

Apparently Tomcat has removed the 8.5.15 tag. So now you can't do docker-compose up -d.

I just changed this line to FROM tomcat:8.5-jre8-alpine in the Fuseki and Fcrepo Dockerfiles.

[birkland]

That is so irritating. I'd like to see if the hash (without the tag) still works. That's the key to reproducible builds, since publishers like Tomcat can and do update images without updating the tag. So somebody who builds on Tuesday could be using completely different Tomcat image than somebody who builds on Friday.

The hash forces the same exact Tomcat image for everybody. Docker allows hashes without tags, but I wanted to include the tag as well, since the hash is opaque. You can't tell what it is/was just by looking at it.

If the hash works, then we may need to convey the tag information in a comment.

[whikloj]

Related:

Step 1/8 : FROM alpine:3.5@sha256:c0537ff6a5218ef531ece93d4984efc99bbf3f7497c0a7726c88e2bb7584dc96
3.5: Pulling from library/alpine
ERROR: Service 'rdfvis' failed to build: manifest verification failed for digest sha256:c0537ff6a5218ef531ece93d4984efc99bbf3f7497c0a7726c88e2bb7584dc96