RE: [PATCH JGIT] Circular references shouldn't be created

>torsdag 17 september 2009 23:40:12 skrev Avery Pennarun
> <apenwarr@gmail.com>:
> > On Thu, Sep 17, 2009 at 3:23 PM, Sohn, Matthias
> <matthias.sohn@sap.com> wrote:
> > >        void link(final String name, final String target) throws
> IOException {
> > > +               if (name.equals(target))
> > > +                       throw new IllegalArgumentException(
> > > +                                       "illegal circular reference
> : symref " + name
> > > +                                                       + " cannot
> refer to " + target);
> >
> > This isn't a very thorough fix.  It doesn't catch longer loops, like
> >
> >     HEAD -> chicken -> HEAD
> >
> > or
> >
> >    a -> b -> c -> d -> a
> >
> > Experimenting with original git.git's implementation, I see that this
> > is allowed:
> >
> >    git symbolic-ref refs/heads/boink refs/heads/boink
> >
> > It succeeds and creates a file that looks like this:
> >
> >    ref: refs/heads/boink
> >
> > And "git show-ref refs/heads/boink" says: nothing (but returns an
> error code).
> >
> > And "git log refs/heads/boink" says:
> >
> >    warning: ignoring dangling symref refs/heads/boink.
> >    fatal: ambiguous argument 'refs/heads/boink': unknown revision or
> > path not in the working tree.
> >    Use '--' to separate paths from revisions
> >
> > Clearly, in git.git, symref loops are caught at ref read time, not
> > write time.  This makes sense, since someone might foolishly twiddle
> > the repository by hand and you don't want to get into an infinite loop
> > in that case.  Also, it's potentially useful to allow people to set
> > invalid symrefs *temporarily*, as part of a multi step process.

> 
> I had already written a patch much like this when I decided we need to
> do much better.
> 
> I think we should do this in the UI by not allowing the user to make a
> choice that would result in a loop and fixing the way the UI resolves
> choices. When creating a new branch we should analyze the selected
> ref and dereference it if it is a symbolic name like HEAD or if it is a
> tag,
> and perhaps show it like "HEAD (refs/heads/master)" in the the dialog.
> 
> Using unresolvable refs as the base for a new branch should be
> disallowed.
>