patchcompletion: fix __gitcomp_builtin no longer consider extra options

> __gitcomp_builtin() has the main completion list provided by
>
>     git xxx --git-completion-helper
>
> but the caller can also add extra options that is not provided by
> --git-completion-helper. The only call site that does this is "git
> difftool" completion.
>
> This support is broken by b221b5ab9b (completion: collapse extra
> --no-.. options - 2018-06-06), which adds a special value "--" to mark
> that the rest of the options can be hidden by default. The commit
> forgets the fact that extra options are appended after
> "$(git xxx --git-completion-helper)", i.e. after this "--", and will
> be incorrectly hidden as well.
>
> Prepend the extra options before "$(git xxx --git-completion-helper)"
> to avoid this.

>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  contrib/completion/git-completion.bash | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
> index db7fd87b6b..c8fdcf8644 100644
> --- a/contrib/completion/git-completion.bash
> +++ b/contrib/completion/git-completion.bash
> @@ -400,7 +400,7 @@ __gitcomp_builtin ()
>  	if [ -z "$options" ]; then
>  		# leading and trailing spaces are significant to make
>  		# option removal work correctly.
> -		options=" $(__git ${cmd/_/ } --git-completion-helper) $incl "
> +		options=" $incl $(__git ${cmd/_/ } --git-completion-helper) "
>  		for i in $excl; do
>  			options="${options/ $i / }"
>  		done

>
> Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:
>
> > __gitcomp_builtin() has the main completion list provided by
> >
> >     git xxx --git-completion-helper
> >
> > but the caller can also add extra options that is not provided by
> > --git-completion-helper. The only call site that does this is "git
> > difftool" completion.
> >
> > This support is broken by b221b5ab9b (completion: collapse extra
> > --no-.. options - 2018-06-06), which adds a special value "--" to mark
> > that the rest of the options can be hidden by default. The commit
> > forgets the fact that extra options are appended after
> > "$(git xxx --git-completion-helper)", i.e. after this "--", and will
> > be incorrectly hidden as well.
> >
> > Prepend the extra options before "$(git xxx --git-completion-helper)"
> > to avoid this.
>
> Thanks for a clear analysis.  How did you find it?  Got annoyed that
> completion of difftool got broken, or discovered while trying to
> apply the same trick as difftool completion uses to another one and
> seeing that the technique does not work?

> On Mon, Oct 22, 2018 at 5:51 AM Junio C Hamano <gitster@pobox.com> wrote:
> >
> > Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:
> >
> > > __gitcomp_builtin() has the main completion list provided by
> > >
> > >     git xxx --git-completion-helper
> > >
> > > but the caller can also add extra options that is not provided by
> > > --git-completion-helper. The only call site that does this is "git
> > > difftool" completion.
> > >
> > > This support is broken by b221b5ab9b (completion: collapse extra
> > > --no-.. options - 2018-06-06), which adds a special value "--" to mark
> > > that the rest of the options can be hidden by default. The commit
> > > forgets the fact that extra options are appended after
> > > "$(git xxx --git-completion-helper)", i.e. after this "--", and will
> > > be incorrectly hidden as well.
> > >
> > > Prepend the extra options before "$(git xxx --git-completion-helper)"
> > > to avoid this.
> >
> > Thanks for a clear analysis.  How did you find it?  Got annoyed that
> > completion of difftool got broken, or discovered while trying to
> > apply the same trick as difftool completion uses to another one and
> > seeing that the technique does not work?
> 
> I was fixing format-patch completion and was surprised it did not work
> as expected. Never really used difftool myself :P I only found out
> about it when I asked myself "why wasn't this breakage found earlier?"