Allow combination of filter and topology in exec command

[steiler]

close #1728

[steiler]

We should maybe error out if neither topofile nor labels are provided?!

[steiler]

mava@server01:~/projects/containerlab3$ sudo bin/containerlab exec --label clab-node-name=ext1 --cmd "ip link show dev eth1"
Error: none or more than one topology files found, can't auto select one

the issue with the ext containers is, that we are always trying to load a topo file...

[hellt]

I wonder if we should rather ditch topo from this command at all.
Can't we just rely on node labels to invoke commands?

[steiler]

To me the remark here #1728 was quite valid, handing in a topology file and a label for a certain kind shold limit to nodes within the topo that have a certain kind ...
But it seems with all the automagic we build around this kind of combination ext container and label selection is non-trivial.

[steiler]

One could argue that external containers should proabably be handled outside of clab ... and we declare this now a nono use-case

[hellt]

@steiler but don't we have enough labels to select both the topology name and node kind name?

What I am thinking about is

exec --label clab-topo-name=foo --label clab-kind-name=bar

to basically rely on labels to filter out the container to run exec on.

Maybe for ext-containers this is more difficult as they might not even be tagged unless we load the topology and read those fake nodes into the nodes list

[hellt]

I unblocked this PR, and made it to work with and without a topo file, which unblocked ext-container tests.

[codecov]

Codecov Report

Merging #1729 (2401c4b) into main (f03b6fa) will increase coverage by 0.23%.
Report is 5 commits behind head on main.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1729      +/-   ##
==========================================
+ Coverage   51.62%   51.85%   +0.23%     
==========================================
  Files         143      143              
  Lines       13810    13845      +35     
==========================================
+ Hits         7129     7179      +50     
+ Misses       5891     5866      -25     
- Partials      790      800      +10     

Files	Coverage Δ
cmd/exec.go	72.52% <100.00%> (+3.01%)	⬆️
cmd/root.go	74.76% <100.00%> (-1.94%)	⬇️

... and 12 files with indirect coverage changes

[steiler]

/lgtm