cmd/validate-krew-manifest: initial implementation

[ahmetb]

This tool takes a manifest file and runs certain validation steps. It's meant
to test plugin manifests added to krew-index install correctly (so far it has
found one broken manifest).

Fixes #148.
Related to #149 but doesn't fix it.

[codecov-io]

Codecov Report

Merging #151 into master will decrease coverage by 1.99%.
The diff coverage is 37.63%.

@@           Coverage Diff           @@
##           master     #151   +/-   ##
=======================================
- Coverage   52.91%   50.91%   -2%     
=======================================
  Files          12       13    +1     
  Lines         618      711   +93     
=======================================
+ Hits          327      362   +35     
- Misses        240      297   +57     
- Partials       51       52    +1

Impacted Files	Coverage Δ
pkg/index/validate.go	94.11% <ø> (ø)	⬆️
cmd/validate-krew-manifest/main.go	37.63% <37.63%> (ø)

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[ahmetb]

cc: @juanvallejo
this is currently hacky but it'll help us validate issues in submitted manifest files.

[juanvallejo]

@ahmetb trying this out locally. Currently running into the following error:

$ go run cmd/validate-krew-manifest/main.go --manifest="~/gopaths/plugins/src/github.com/GoogleContainerTools/krew-index/plugins/change-ns.yaml"
I0204 13:36:44.913634   15279 main.go:57] structural validation OK
I0204 13:36:44.913756   15279 main.go:65] all spec.platform[] items are used
I0204 13:36:44.913850   15279 main.go:71] no overlapping spec.platform[].selector
I0204 13:36:44.913857   15279 main.go:75] installing spec.platform[0]
F0204 13:36:44.990111   15279 main.go:39] spec.platforms[0] failed to install: plugin install command failed: Error: unknown command "krew" for "kubectl"
        Run 'kubectl --help' for usage.
        unknown command "krew" for "kubectl"
        : exit status 1
exit status 255

[ahmetb]

@juanvallejo you need to install krew first. The validator runs kubectl krew install with KREW_OS, KREW_ARCH for each spec.platform[] and with a temp KREW_ROOT dir to see if installation goes through.

For example, the install failed to symlink "change-ns" on windows, because the bin field for windows was lacking the .exe suffix.

[juanvallejo]

@ahmetb yep thanks, had some path issues with kubectl. Appears to be working now

[ahmetb]

Ideally we'd take some of the validation here (like "has overlapping platform selectors", "all selectors map to at least one supported os/arch") and put it in pkg/index#Validate() method in the future –so there's one path for validation.

[juanvallejo]

lgtm