wrap: Avoid trailing whitespace for empty lines

[abitrolly]

What type of PR is this?

• bug

What this PR does / why we need it:

Linter tools are picky about trailing whitespace, which creates problems when --help output is used in documentation and tests (sourcegraph/scip#97).

Which issue(s) this PR fixes:

(REQUIRED)

Testing

(fill-in or delete this section)

Release Notes

(REQUIRED)

[abitrolly]

@julian7 any hints why test stared to fail after implementing the last suggestion? There is an extra line generated with that code.

Got:

        NAME:
           
         - add a task to the list
        
        USAGE:
           this is an even longer way
           of describing adding a task
           to the list
        
        DESCRIPTION:
           and a description long
           enough to wrap in this test
           case
        
        OPTIONS:
           --help, -h  show help (default: false)

Expected:

        NAME:
            - add a task to the list
        
        USAGE:
           this is an even longer way
           of describing adding a task
           to the list
        
        DESCRIPTION:
           and a description long
           enough to wrap in this test
           case
        
        OPTIONS:
           --help, -h  show help (default: false)

My only guess that something passes string that is not trimmed to wrap. But I don't see how wrap trimmed the string before. What changes though, is that if an empty string is passed to it, now the newline is returned. Could it be the case?

[abitrolly]

I refactored code to use slice instead of string buffer. PTAL.

[dearchap]

@abitrolly Thank you for the PR. Help output is extremely fragile due to the newlines and white spaces etc. The wrap along with the template generates the output and even a slight change in template can create different outputs. If the tests pass that is good enough to merge. Just a heads up though that I have a PR #1506 which fixes a "similar" issue. Please review that as well. Thanks

[dearchap]

Excellent thanks

Changes committed