Fix URL with encoded path support for ChartDownloader

[sathieu]

What this PR does / why we need it:

When the repo url contains URL-encoded parts, and doesn't end with /, relative downloads are not properly resolved.

Example, with current main (3d1bc72):

$ bin/helm repo add kubitus-ingress-operator https://gitlab.com/api/v4/projects/kubitus-project%2Fkubitus-ingress-operator/packages/helm/stable
"kubitus-ingress-operator" has been added to your repositories

$ show.go:173: [debug] Original chart version: ""
Error: failed to fetch https://gitlab.com/api/v4/projects/kubitus-project/kubitus-ingress-operator/packages/helm/stable/charts/kubitus-ingress-operator-v0.2.0.tgz : 404 Not Found
helm.go:81: [debug] failed to fetch https://gitlab.com/api/v4/projects/kubitus-project/kubitus-ingress-operator/packages/helm/stable/charts/kubitus-ingress-operator-v0.2.0.tgz : 404 Not Found
helm.sh/helm/v3/pkg/getter.(*HTTPGetter).get
        /home/circleci/helm.sh/helm/pkg/getter/httpgetter.go:73
helm.sh/helm/v3/pkg/getter.(*HTTPGetter).Get
        /home/circleci/helm.sh/helm/pkg/getter/httpgetter.go:41
helm.sh/helm/v3/pkg/downloader.(*ChartDownloader).DownloadTo
        /home/circleci/helm.sh/helm/pkg/downloader/chart_downloader.go:99
helm.sh/helm/v3/pkg/action.(*ChartPathOptions).LocateChart
        /home/circleci/helm.sh/helm/pkg/action/install.go:675
main.runShow
        /home/circleci/helm.sh/helm/cmd/helm/show.go:179
main.newShowCmd.func4
        /home/circleci/helm.sh/helm/cmd/helm/show.go:116
github.com/spf13/cobra.(*Command).execute
        /go/pkg/mod/github.com/spf13/cobra@v1.1.1/command.go:850
github.com/spf13/cobra.(*Command).ExecuteC
        /go/pkg/mod/github.com/spf13/cobra@v1.1.1/command.go:958
github.com/spf13/cobra.(*Command).Execute
        /go/pkg/mod/github.com/spf13/cobra@v1.1.1/command.go:895
main.main
        /home/circleci/helm.sh/helm/cmd/helm/helm.go:80
runtime.main
        /usr/local/go/src/runtime/proc.go:204
runtime.goexit
        /usr/local/go/src/runtime/asm_amd64.s:1374

As you can see, %2F was replaced by / which leads to 404 Not found.

We this patch applied, it works:

$ bin/helm show chart  kubitus-ingress-operator/kubitus-ingress-operator --debug
show.go:195: [debug] Original chart version: ""
apiVersion: v2
appVersion: main
dependencies:
- condition: metacontroller.enabled
  name: metacontroller
  repository: ""
description: Kubitus Ingress Operator
home: https://gitlab.com/kubitus-project/kubitus-ingress-operator
name: kubitus-ingress-operator
sources:
- https://gitlab.com/kubitus-project/kubitus-ingress-operator
type: application
version: v0.2.0

Special notes for your reviewer:

Fixes: #9977.

If applicable:

• this PR contains documentation
• this PR contains unit tests
• this PR has been tested for backwards compatibility

[sathieu]

@cndoit18 Please review this one (split out of #9763).

[sathieu]

@mattfarina Please review this other fix about encoded slashes (similar to PR #9822).

[ghost]

LGTM. Thank you for the fix!

[sathieu]

@cndoit18 Please review again.

[sathieu]

@bacongobbler Please review 🙏.

[sathieu]

@hickeyma Please review 🙏.

[sathieu]

@cndoit18 @bacongobbler Please review again. I've rebased and fixed conflicts.

[sathieu]

@cndoit18 @bacongobbler Could you please take some time to review this PR?

[sathieu]

This PR is now 10 months old. Could it be added to the 3.9 milestone to ensure it is reviewed? 🙏

[sathieu]

This PR is now 1 year old. Any chance to get it reviewed and hopefully merged 🍀 ?

[hickeyma]

LGTM, thanks @sathieu

[hickeyma]

This will need another Helm maintainer to review before merging.

[sathieu]

Thanks @hickeyma Would you please ping an available maintainer?

[sathieu]

Thanks @mattfarina 🙏 !