Add the --target flag as a parameter to the docker builder.

[dlorenc]

Fixes #635

[codecov-io]

Codecov Report

Merging #894 into master will increase coverage by 0.14%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #894      +/-   ##
==========================================
+ Coverage   39.38%   39.52%   +0.14%     
==========================================
  Files          61       61              
  Lines        2613     2616       +3     
==========================================
+ Hits         1029     1034       +5     
+ Misses       1471     1469       -2     
  Partials      113      113

Impacted Files	Coverage Δ
pkg/skaffold/build/local/docker.go	21.05% <ø> (+2%)	⬆️
pkg/skaffold/docker/image.go	59.18% <100%> (+2.19%)	⬆️

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[dgageot]

@dlorenc there’s much more required to support —target. Local builder has two modes, support needs to be added to gcb and kaniko too, and the computation of the build context should also be updated.

[dlorenc]

Yeah sorry, this needs a WIP tag. I got sidetracked checking to see if kaniko supports the target flag yet.

Can you explain the build context part a little more though? Is that an optimization because some of the build context might not be needed based on the target?

[dlorenc]

@dgageot can you explain what you mean by the local builder having two modes? Are you referring to the docker API vs. docker binary?

[dlorenc]

ping @dgageot I think I actually did this correctly by accident.

There will be a small change in behavior, but I'm not sure what's correct. Previously if someone specified --cache-from with Kaniko, it would be ignored. Now it'll be an error.

[dgageot]

Minor nit. Other than that, LGTM!

[dgageot]

WDYT of inlining args? Since it contains a single arguments, I think it makes sense.
Also, most tests use description instead of name to describe the test.

[dlorenc]

Done, this is the pattern the vs-code test generator thing uses by default, but I agree it's overkill

[dgageot]

@dlorenc you are right that you had it right the first time. I read your PR too quickly. Sorry

[dlorenc]

@dlorenc you are right that you had it right the first time. I read your PR too quickly. Sorry

It was definitely by accident :) I didn't realize the GetBuildArgs function was used everywhere, luckily it works.

[dgageot]

@dlorenc linter is failing