Re: Question about '[,']!filter versus %!filter (in autocmd)

Tony Mechelynck wrote:

> On Tue, Dec 22, 2015 at 1:44 AM, <raf@raf.org> wrote:
> > Hi,
> >
> > I found the following auto commands somewhere for using gnupg:
> >
> > " Transparent editing of gpg encrypted files.
> > " By Wouter Hanegraaff
> > augroup encrypted
> > au!
> >
> > " First make sure nothing is written to ~/.viminfo while editing
> > " an encrypted file.
> > autocmd BufReadPre,FileReadPre *.gpg set viminfo=
> > " We don't want a various options which write unencrypted data to disk
> > autocmd BufReadPre,FileReadPre *.gpg set noswapfile noundofile nobackup
> >
> > " Switch to binary mode to read the encrypted file
> > autocmd BufReadPre,FileReadPre *.gpg set bin
> > autocmd BufReadPre,FileReadPre *.gpg let ch_save = &ch|set ch=2
> > " (If you use tcsh, you may need to alter this line.)
> > autocmd BufReadPost,FileReadPost *.gpg '[,']!gpg --decrypt 2> /dev/null
> >
> > " Switch to normal mode for editing
> > autocmd BufReadPost,FileReadPost *.gpg set nobin
> > autocmd BufReadPost,FileReadPost *.gpg let &ch = ch_save|unlet ch_save
> > autocmd BufReadPost,FileReadPost *.gpg execute ":doautocmd BufReadPost " . expand("%:r")
> >
> > " Convert all text to encrypted text before writing
> > " (If you use tcsh, you may need to alter this line.)
> > autocmd BufWritePre,FileWritePre *.gpg '[,']!gpg --default-recipient-self -ae 2>/dev/null
> > " Undo the encryption so we are back in the normal text, directly
> > " after the file has been written.
> > autocmd BufWritePost,FileWritePost *.gpg u
> > augroup END
> >
> > This is very similar to the script at http://vim.wikia.com/wiki/Edit_gpg_encrypted_files
> > where, in the discussion, someone comments that they don't understand why '[,']!gpg
> > was used instead of %!gpg.
> >
> > Can anyone explain this? '[,'] refers to the previously changed or yanked
> > text whereas % refers to the entire file (which is what is wanted).
> >
> > Will '[,'] always refer to the entire file in the autocommands above?
> > If so, how so? Would it be better with % or identical?
> >
> > I can see that it would refer to the entire file in the BufReadPost,FileReadPost
> > state because the entire file has just been read so the last "change" is the entire
> > file but what about the BufWritePre,FileWritePre state?
> >
> > I should say that saving works even if I have changed or yanked part of the
> > file immediately before saving. I just don't know why it works.
> >
> > cheers,
> > raf
>
> The % range is a shortcut for 1,$ which means "first line to last
> line". OTOH, using an unabbreviated range lets you use the full power
> of "how to define a line". In :'[,']!filter, the range goes from the [
> mark to the ] mark, i.e. from the line containing the first character
> of the latest change or yank, to the line containing the last one. At
> the BufReadPost and FileReadPost autocommands, the last operation on
> the file consisted of reading it in, so that "the text latest changed"
> is the whole file. Even if the viminfo is used to keep a file's mark
> from one session to the next, the '[ and '] marks are not saved: see
> the help mentioned below.
>
> See:
> :help :range
> :help '[
> :help ']
> :help viminfo-file-marks
> and also the full section starting at
> :help mark-motions
>
>
> Best regards,
> Tony.

Sorry. I thought I had explained that I understood why it worked
in the BufReadPre,FileReadPre autocmds.

What I am asking is: why is it that '[,'] refers to the whole file
in the BufWritePre,FileWritePre autocmd when, according to the
documentation that I've read, it should only refer to the last
changed or yanked text.

In other words, If I yank or change a part of the file immediately
before saving, why do these write autocmds encrypt the entire file
and not just the text that was changed or yanked. It is behaving
as though the markers have been reset somehow before the write
autocmds have executed.

Can anyone explain that?

cheers,
raf

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