context: put quotes around flagvalue incase of whitespaced values

[ataberkgrl]

Resolves #541

While running the sync command it starts to generate cp commands in the generateCommand function and writes it to a pipe where it is read by the Run function of the Run command. In the Run function, there is a line

fields, err := shellquote.Split(line)

to split the generated cp command into its fields.



 For a command





s5cmd sync --cache-control ‘public, max-age=31536000, immutable’ /Users/ataberk/desktop/test s3://s5cmd-test2

We would have expected the generateCommand function to write into the pipe a command



cp --cache-control='public, max-age=31536000, immutable' --raw='true' \"/Users/ataberk/desktop/test/hello.txt\" \"s3://s5cmd-test2/test/hello.txt\"

But instead, it writes the command



cp --cache-control=public, max-age=31536000, immutable --raw=true \"/Users/ataberk/desktop/test/hello.txt\" \"s3://s5cmd-test2/test/hello.txt\"

This causes the shellquote.Split(line) to split fields incorrectly. This causes flagset.Parse(fields) to populate flagset incorrectly and as a result we end up with an error.

The main problem occurs in the generateCommand function while appending flags without quotes. If we add quotes around the flagValue while generating a command. The shellquote.Split(line) acts as intended and successfully sync with the given cache-control metadata in S3

[sonmezonur]

Thanks for the PR! Could you please add a test for your use case? (example command you shared)

[7rulnik]

Thanks, guys ❤️