Fix bug in sync

[priyawadhwa]

This PR fixes a bug in sync, in which desinations for synced files were
being calculated incorrectly. For the hot-reload example, app.py was
being synced to /src/app.py instead of /app.py, so it appeared as if
sync wasn't actually working.

To fix this issue, I fixed a bug in the intersect function to make sure
destination calculation follows the Docker COPY command rules.

For example, we had a unit test as follows:

syncMap: **/**/*.js": "."
file: dir1/dir2/node.js
dst: /dir1/dir2/node.js

I think the destination should actually be /node.js based on Docker COPY
command rules.

should fix #1668

[codecov-io]

Codecov Report

Merging #1709 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1709   +/-   ##
=======================================
  Coverage   47.05%   47.05%           
=======================================
  Files         126      126           
  Lines        6142     6142           
=======================================
  Hits         2890     2890           
  Misses       2961     2961           
  Partials      291      291

Impacted Files	Coverage Δ
pkg/skaffold/sync/sync.go	91.3% <100%> (ø)	⬆️

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[codecov-io]

Codecov Report

Merging #1709 into master will decrease coverage by 0.14%.
The diff coverage is 56.25%.

@@            Coverage Diff             @@
##           master    #1709      +/-   ##
==========================================
- Coverage   47.05%   46.91%   -0.15%     
==========================================
  Files         126      126              
  Lines        6142     6167      +25     
==========================================
+ Hits         2890     2893       +3     
- Misses       2961     2976      +15     
- Partials      291      298       +7

Impacted Files	Coverage Δ
pkg/skaffold/docker/image.go	58.38% <0%> (ø)	⬆️
pkg/skaffold/docker/remote.go	24.24% <0%> (ø)	⬆️
pkg/skaffold/sync/sync.go	75.28% <60%> (-16.03%)	⬇️
hack/schemas/main.go	87% <0%> (-3.12%)	⬇️

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[dgageot]

I'm not sure I agree. Let me think about it before it's merged

[dgageot]

There seems to be an issue with name.ParseReference(target, name.WeakValidation). It fails to parse gcr.io/k8s-skaffold/test-file-sync:67738fe@sha256:13e30612be9aa5dae72fb06619ff0dabf80ca600e8f949da683abe73d2f0113b even if it's a correct image reference.

cc @jonjohnsonjr

[priyawadhwa]

@dgageot @balopat I just pushed a workaround to remove the tag and use just the digest for getting the workingDir from the image until go-containerregistry can parse both.

[nkubala]

@priyawadhwa I think that's fine, can you check out the failing test in Kokoro though? doesn't look like a flake

[jonjohnsonjr]

google/go-containerregistry#351

I kind of have a philosophical disagreement with that format of reference. I think it's misleading.

I'm happy to take a PR to fix it, I just don't have time to figure out the regex voodoo myself.