helm fetch fails on chart with special character in version

[bzbikowski]

Hi,

I've run into an issue with helm fetch/install when I've tried to access the chart with a special character in its version, in my case plus sign ('+'). Helm search was working without issue but fetch/install was throwing 404 error. The helm repo in the S3 bucket was set using the helm-s3 plugin, the chart was pushed using the plugin, but the repo in helm was set using the HTTPS path, not s3://bucket-name/path.

Reason:
S3 expects that some of the special characters will be encoded in the URL when trying to access the files over HTTP.
For example, '+' in the URL must be changed to '%2B'.
GET https://s3.Region.amazonaws.com/bucket-name/charts/chart-1.0.0+100.tgz -> 404 Not Found
GET https://s3.Region.amazonaws.com/bucket-name/charts/chart-1.0.0%2B100.tgz -> 200 Ok

Solution:
During artifact push, when updating index.yaml file, encode in URL section special characters (only tested on '+', the list might be bigger, it might be connected to https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-keys.html).

Steps to reproduce:

1. Create a bucket and init a helm repo with helm-s3 plugin
2. Change the version of your chart to include a special character (in my case '+') e.g. 1.0.0+100
3. Build and push this chart to the bucket using helm-s3 plugin
4. Add repo using path-style URL e.g. https://s3.Region.amazonaws.com/bucket-name/charts
5. Fetch chart from HTTPS repo

Environment:
Helm version: v3.8.0
Helm-s3 plugin version: v.0.10.0