Adding drsview to pipe producers

[bnlawrence]

The idea here is that we want to be able to go from a drsview to specific files (this was possible before, but this is an exercise in building up the piping infrastructure as well as adding a different route to functionality).

[Copilot]

Pull request overview

This pull request adds piping infrastructure to enable chaining commands together using the :: operator, specifically allowing drsview to pipe its output to other commands like ls. The implementation includes caching mechanisms to avoid expensive recomputation and adds defensive null-checking throughout the codebase.

Changes:

• Added drsview to pipe producers and ls to pipe consumers
• Implemented output caching in do_drsview to support piping
• Enhanced do_ls to consume piped input from other commands
• Added defensive null checks for object attributes throughout the codebase
• Made docker dependency optional for tests that don't require MinIO

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 16 comments.

File	Description
tests/test_piping.py	New test file covering pipe functionality between drsview and ls commands
tests/conftest.py	Made docker import optional to allow running tests without Docker installed
pyproject.toml	Added udunits2 as a new dependency
cfs3/s3cmd.py	Core implementation of piping infrastructure, output caching, and defensive programming enhancements

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[valeriupredoi]

looks like you're in decent hands here @bnlawrence 😆

[bnlawrence]

I accidentally put the #22 over top of this rather than branch, and it's too much hassle to unpick , so we'll pick this up there.