fix: ignore concurrency if not specified

[gsquared94]

Fixes: #7181

Description

The build concurrency should be set to the minimum defined concurrency across all configs. Previously, imported configs that didn't define concurrency were defaulting to the value of 1, thereby lowering the overall concurrency to 1.
We remove setting this default value in the config, rather if the resolved build concurrency is defaulted to 1 at the end.

Testing instructions

• In project examples/multi-config-microservices set the root skaffold.yaml config's build concurrency.

apiVersion: skaffold/v2beta28
kind: Config
build:
  local:
    concurrency: 2
requires:
- path: ./leeroy-app
- path: ./leeroy-web

• Run skaffold build -v DEBUG. The output should have the following log lines showing that the build concurrency was updated to that value:

INFO[0000] build concurrency first set to 2 parsed from *local.Builder[3]  subtask=-1 task=DevLoop
INFO[0000] final build concurrency value is 2            subtask=-1 task=DevLoop

[codecov]

Codecov Report

Merging #7182 (b8639f2) into main (290280e) will decrease coverage by 2.00%.
The diff coverage is 56.96%.

@@            Coverage Diff             @@
##             main    #7182      +/-   ##
==========================================
- Coverage   70.48%   68.47%   -2.01%     
==========================================
  Files         515      560      +45     
  Lines       23150    26461    +3311     
==========================================
+ Hits        16317    18119    +1802     
- Misses       5776     7090    +1314     
- Partials     1057     1252     +195     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/deploy.go	52.00% <ø> (-1.85%)	⬇️
cmd/skaffold/app/cmd/dev.go	84.61% <0.00%> (ø)
cmd/skaffold/app/cmd/render.go	36.66% <0.00%> (-4.72%)	⬇️
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/lsp.go	28.12% <28.12%> (ø)
cmd/skaffold/app/cmd/fix.go	68.85% <40.00%> (-7.62%)	⬇️
cmd/skaffold/app/cmd/lint.go	42.85% <42.85%> (ø)
cmd/skaffold/app/cmd/find_configs.go	48.88% <50.00%> (+0.24%)	⬆️
cmd/skaffold/app/skaffold.go	76.19% <70.00%> (-8.43%)	⬇️
... and 223 more

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[briandealwis]

WDYT about extracting the minConcurrency logic into a separately testable function?

[briandealwis]

Add that 0 merits special treatment: if there are two configs A and B, and A has concurrency 0 and B has concurrency 1, then the "minimum" should be 1 since it's the most stringent.

[briandealwis]

This doesn't seem to be equivalent. Consider if I have two modules, A and B. Both have local build-envs. A does not specify a build concurrency. B specified concurrency 0. I believe that prior to this change, A would have had a default concurrency of 1 set which would have resulted in the minConcurrency==1 (serialized). Whereas now A would be skippedI think we will have minConcurrency 0.

Honestly, I think we should separate this out into a function whose results can be tested for different scenarios.

[tejal29]

@briandealwis I verified via this test here that if B specified concurrency 0 and A does not set the concurrency, then it default to 1.

[MarlonGamez]

don't have much to add that brian didn't already catch