indentation on verbose tracing

[dhduvall]

While working on fatih/vim-go#2090, I was having a bit of trouble tracking down where &cpo wasn't getting reset properly. I ended up doing this:

$ vim -V99trace.out foo.go
...
$ awk '/cpo/ {
    printf("%*s%s\n", i * 2, "", $0)
}
$0 ~ /^sourcing|^line [0-9]*: sourcing/ && $0 !~ /finished/ {
    printf("\n%*s%s\n", i * 2, "", $0); i++
}
/^finished sourcing/ {
    i--; printf("%*s%s\n", i * 2, "", $0)
}' trace.out

which gave me some nice indented trace output:

sourcing "$VIM/vimrc"

  line 10: sourcing "/usr/share/vim/vim81/debian.vim"
  finished sourcing /usr/share/vim/vim81/debian.vim
finished sourcing $VIM/vimrc

sourcing "$HOME/.vimrc"
  line 9: set cpoptions+=$

  line 130: sourcing "/home/duvall/.vim/autoload/pathogen.vim"
  finished sourcing /home/duvall/.vim/autoload/pathogen.vim

  line 150: sourcing "/usr/share/vim/vim81/filetype.vim"
    line 12: " Line continuation is used here, remove 'C' from 'cpoptions'
    line 13: let s:cpo_save = &cpo
    line 14: set cpo&vim

    line 2121: sourcing "/home/duvall/.vim/bundle/vim-go/ftdetect/gofiletype.vim"
      line 4: let s:cpo_save = &cpo
      line 5: set cpo&vim
      line 63: let &cpo = s:cpo_save
      line 64: unlet s:cpo_save
    finished sourcing /home/duvall/.vim/bundle/vim-go/ftdetect/gofiletype.vim
    line 2159: " Restore 'cpoptions'
    line 2160: let &cpo = s:cpo_save
    line 2161: unlet s:cpo_save
  finished sourcing /usr/share/vim/vim81/filetype.vim

It'd be nice to have something like this built-in to help navigate the rats nest of included vim scripts, though I can understand if it's too specific and finicky to implement generally. In that case, perhaps this issue can serve to document the awk command for others.