Re: [PATCH v3] pathspec: advice: long and short forms are incompatible

>
> Stavros Ntentos <stdedos@gmail.com> writes:
>
> > It can be a "reasonable" mistake to mix short and long forms,
> > e.g. `:!(glob)`, instead of the (correct) `:(exclude,glob)`.
>
> The word "form" may be sufficient for today's us because we have
> been so focused on this particular pathspec magic issue.
>
> But reviewers are not, and those who read the "git log" output later
> are not, either.  Let's be friendly and helpful to them by saying
> "form of pathspec magic" or somesuch.
>
> The same comment applies to the patch title.
>
> It also might be more friendly to readers what the mistaken form
> would do, too.
>
> Here is my attempt, taking all of the above into account.
>
>     It is a hard-to-notice mistake to try mixing short and long
>     forms of pathspec magic, e.g. instead of ':(exclude,glob)', it
>     may be tempting to write ':!(glob)', which stops at ":!",
>     i.e. the end of the short-form pathspec magic, and the "(glob)"
>     is taken as the beginning part of the pathspec, wanting to match
>     a file or a directory whose name begins with that literal string.
>
> > Teach git to issue an advice when such a pathspec is given.
> >         i.e.: While in short form parsing:
> >         * if the string contains an open parenthesis [`(`], and
> >         * without having explicitly terminated magic parsing (`:`)
> >         issue an advice hinting to that fact.
>
> OK.
>
> > Based on "Junio C Hamano <gitster@pobox.com>"'s code suggestions:
> > * https://lore.kernel.org/git/xmqqa6qoqw9n.fsf@gitster.g/
> > * https://lore.kernel.org/git/xmqqo8f0cr9z.fsf@gitster.g/
>
> It is sufficient to just write a single line
>
>         Helped-by: Junio C Hamano <gitster@pobox.com>
>
> immediately before your sign-off, I would think.
>
> > Signed-off-by: Stavros Ntentos <133706+stdedos@users.noreply.github.com>
>
> The sign-off name and address must match the name and address of the
> patch author (i.e. "Stavros Ntentos <stdedos@gmail.com>").
>
> > +     mixedPathspecMagic::
> > +             Advice shown if a user tries to mix short- and
> > +             longform pathspec magic.
>
> Good.  Here the phrase "pathspec magic" is used.
>
> > +/*
> > + * Give hint for a common mistake of mixing short and long
> > + * form of pathspec magic, as well as possible corrections
> > + */
> > +static void warn_mixed_magic(unsigned magic, const char *elem, const char *pos)
> > +{
> > +     struct strbuf longform = STRBUF_INIT;
> > +     int i;
> > +
> > +     if (!advice_enabled(ADVICE_MIXED_PATHSPEC_MAGIC))
> > +             return;
> > +
> > +     for (i = 0; i < ARRAY_SIZE(pathspec_magic); i++) {
> > +             if (pathspec_magic[i].bit & magic) {
> > +                     if (longform.len)
> > +                             strbuf_addch(&longform, ',');
> > +                     strbuf_addstr(&longform, pathspec_magic[i].name);
> > +             }
> > +     }
>
> OK, so we are collecting the ones given by the short form so far.
> For e.g. ":!(glob)", we write "exclude" in the longform buffer.  If
> we had more than one, then before adding the second one, we add a
> comma, so we may see "top,exclude" for ":/!(glob)".  Good.
>
> > +     advise_if_enabled(ADVICE_MIXED_PATHSPEC_MAGIC,
> > +                       _("'%.*s(...': cannot mix short- and longform pathspec magic!\n"
>
> Do we need to "shout!"?  I think a normal full-stop would be sufficient.
>
> 'elem' is pointing at ':', 'pos' is where we read '(' from, so
> the above gives us "':/!(...': cannot..." for "':/!(glob)".  OK.
>
> > +                         "Either spell the shortform magic '%.*s' as ':(%s,...'\n"
>
> Here, the shortform %.*s excludes the ':' that introduced the magic,
> so we would see "shortform magic '/!' as ':(top,exclude,...'".  Good.
>
> > +                         "or end magic pathspec matching with '%.*s:'."),
>
> This one I am not sure about.  Something like
>
>     $ git add -- ":!(0) preface.txt" \*.txt
>
> may be plausible, albeit rare, and it may be a good advice to
> explicitly terminate the shortform pathspec magic before the '(' in
> such a case.
>
> But presumably it is much rarer for '(' to be a part of a pathspec
> element than an attempt to introduce a longform magic, it might be
> worth spending an extra line to explain in what narrow cases the
> latter choice may make sense.  Here is my attempt.
>
>     or if '(...' is indeed the beginning of a pathname, end the shortform
>     magic sequence explicitly with another ':' before it, e.g. '%.*s:(...'
>
>
> > +                       (int)(pos - elem), elem,
> > +                       (int)(pos - (elem + 1)), elem + 1,
> > +                       longform.buf,
> > +                       (int)(pos - elem), elem);
> > +}
> >  /*
> >   * Parse the pathspec element looking for short magic
> >   *
> > @@ -356,6 +386,9 @@ static const char *parse_short_magic(unsigned *magic, const char *elem)
> >                       continue;
> >               }
> >
> > +             if (ch == '(')
> > +                     warn_mixed_magic(*magic, elem, pos);
> > +
> >               if (!is_pathspec_magic(ch))
> >                       break;
> >
> > diff --git a/t/t6132-pathspec-exclude.sh b/t/t6132-pathspec-exclude.sh
> > index 30328b87f0..8b9d543e1e 100755
> > --- a/t/t6132-pathspec-exclude.sh
> > +++ b/t/t6132-pathspec-exclude.sh
> > @@ -244,4 +244,42 @@ test_expect_success 'grep --untracked PATTERN :(exclude)*FILE' '
> >       test_cmp expect-grep actual-grep
> >  '
> >
> > +cat > expected_warn <<"EOF"
> > +hint: ':!(...': cannot mix short- and longform pathspec magic!
> > +hint: Either spell the shortform magic '!' as ':(exclude,...'
> > +hint: or end magic pathspec matching with ':!:'.
> > +hint: Disable this message with "git config advice.mixedPathspecMagic false"
> > +EOF
> > +test_expect_success 'warn pathspec not matching longform magic in :!(...)' '
> > +     git log --oneline --format=%s -- '"'"':!(glob)**/file'"'"' >actual 2>warn &&
> > +     cat <<EOF >expect &&
> > +sub2/file
> > +sub/sub/sub/file
> > +sub/file2
> > +sub/sub/file
> > +sub/file
> > +file
> > +EOF
> > +     cat actual &&
> > +     cat warn &&
>
> Are these leftover debugging aid?
>
> > +     test_cmp expect actual &&
> > +     test_cmp expected_warn warn
> > +'
> > +
> > +test_expect_success 'do not warn pathspec not matching longform magic in :!:(...) (i.e. if magic parsing is explicitly stopped)' '
> > +     git log --oneline --format=%s -- '"'"':!:(glob)**/file'"'"' >actual 2>warn &&
> > +     cat <<EOF >expect &&
> > +sub2/file
> > +sub/sub/sub/file
> > +sub/file2
> > +sub/sub/file
> > +sub/file
> > +file
> > +EOF
> > +     cat actual &&
> > +     cat warn &&
>
> Are these leftover debugging aid?
>
> > +     test_cmp expect actual &&
> > +     ! test_cmp expected_warn warn
> > +'
> > +
> >  test_done
>
>
> Thanks.