Fix multiline copyright header rule

[krwq]

Fix a problem where some lines of multiline header are repeated during the formatting already formmated code.

I.e:

// test1
// test2

was formatted to:

// test1
// test2

// test1
// test2

When using real headers some of those lines are removed as they are treated as "old" header. I.e:

// Copyright blah
// License X

was being formatted to:

// Copyright blah
// License X

// License blah

[krwq]

I just found an issue with that, doesn't work correctly with:

// Copyright blah
// License X

// My Comment

[krwq]

Above is fixed in the updated PR.

[krwq]

Above fixes the issue where there are whitespaces after the comment in the header (really rare but could happen).

[krwq]

Hi @jaredpar, could you take a look at this PR?

[jaredpar]

👍

Thanks for fixing that.