Re: [PATCH] object-name: fix reversed ordering with magic pathspecs

[Patrick Steinhardt <ps@pks.im>]

On Fri, Dec 06, 2024 at 08:57:04PM +0900, Junio C Hamano wrote:
> "Kristoffer Haugsbakk" <kristofferhaugsbakk@fastmail.com> writes:
> 
> > On Fri, Dec 6, 2024, at 10:51, Patrick Steinhardt wrote:
> >> It was reported
> >
> > It would be nice with a hyperlink since this email is not part of the
> > email thread for the report.
> >
> > https://lore.kernel.org/git/Z1LJSADiStlFicTL@pks.im/T/#mae906ec74d5657e702165e29b90927f730280c29
> >
> >> It was reported that magic pathspecs started to return results in
> >
> > I’m not used to this being called “magic pathspecs” as a user.
> > gitglossary(7) talks about (magic) pathspecs as filepaths.
> 
> Thanks for catching the mistaken phrasing.  It would have caused
> unnecessary confusion later to "git log" readers.
> 
> The syntax to say that the following path is from the top-level of
> the working tree even when you are running the command from a
> subdirectory, e.g.
> 
>     cd Documentation
>     git log :/t
> 
> is described in gitglossary(7):
> 
>     A pathspec that begins with a colon `:` has special meaning.  In the
>     short form, the leading colon `:` is followed by zero or more "magic
>     signature" letters (which optionally is terminated by another colon `:`),
>     and the remainder is the pattern to match against the path.
>     The "magic signature" consists of ASCII symbols that are neither
>     alphanumeric, glob, regex special characters nor colon.
>     The optional colon that terminates the "magic signature" can be
>     omitted if the pattern begins with a character that does not belong to
>     "magic signature" symbol set and is not a colon.
> 
> and even though the word "magic" signature is used, there is no
> definition given for the entire construct, i.e. the pathspec that
> uses a special meaning introduced by the use of "colon followed by
> one or more magic signature letters".  We probably should add a
> sentence to officially define it, if only to reduce the need for
> exchanges like this ;-)
> 
>     ... and is not a colon.  Such a pathspec that uses these "magic"
>     meaning is called "magic pathspec".
> 
> But more importantly, the syntax that triggered this topic in
> 
> <CAKOEJdcPYn3O01p29rVa+xv=Qr504FQyKJeSB-Moze04ViCGGg@mail.gmail.com>
> 
> is *NOT* a magic pathspec at all.  It is a revision syntax to name
> the first commit that is reachable from the current HEAD with a
> commit log message, that matches the given patterh, i.e.
> 
>     git show ":/my message"
> 
> which is a (rather lousy) short-hand for a more general
> 
>     git show "HEAD^{/my message}"
> 
> i.e. <startingRev>^{/<pattern>}.  There is no specific name for
> this syntax.

Hm, yeah. I think I read pathspec somewhere and just went with it
without thinking.

> I suspect that "filepath" you mentioned may be something some folks
> (but not me or any other long timers) would call yet another syntax,
> which is :<path>, that names the object sitting at <path> in the
> index.  Because ":/myMessage" look so similar to ":myFile", yet
> they mean so different things, as I said, ":/myMessage" is a rather
> lousy short-hand for the more general "^{/<pattern>}" suffix that
> is less ambiguous.
> 
> Patrick, let's not use a wrong word.  This is not about pathspec at
> all, and is a revision syntax.  As there is no specific jargon for
> the syntax, here is what I would write, if I were explaining the
> problem being solved:
> 
>     Recently it was reported [*1*] that "look for the youngest
>     reachable commit with log message that match the given pattern"
>     syntax (e.g. :/myMessagePattern, or HEAD^{/myMessagePattern})
>     started to show older commit.
> 
>     [Footnote]
>     *1* <CAKOEJdcPYn3O01p29rVa+xv=Qr504FQyKJeSB-Moze04ViCGGg@mail.gmail.com>

Will update in v2. Thanks!

Patrick