Re: [PATCH v4 3/3] cat-file: add --follow-symlinks to --batch

From: David Turner <dturner@twopensource.com>
Date: May 11, 2015, 22:31 UTC
Message-ID: <1431383471.15048.9.camel@ubuntu>
In-Reply-To: <xmqqd2263lxf.fsf@gitster.dls.corp.google.com>

On Mon, 2015-05-11 at 13:21 -0700, Junio C Hamano wrote: dturner@twopensource.com writes:

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> 
> > +--follow-symlinks::
> > +	Follow symlinks inside the repository.  Instead of providing
> > +	output about the link itself, provide output about the linked-to
> > +	object.  This option requires --batch or --batch-check.  In the
> > +	event of a symlink loop (or more than 40 symlinks in a symlink
> > +	resolution chain), the file will be treated as missing.  If a
> > +	symlink points outside the repository (e.g. a link to /foo or a
> > +	root-level link to ../foo), the portion of the link which is
> > +	outside the repository will be printed.  Follow-symlinks will
> > +	be silently turned off if <object> specifies an object in the
> > +	index rather than one in the object database.
> 
> One thing that I found is missing from the above and other places in
> the documents updated by this patch, when I pretend that I am an
> end-user who never saw the discussion for the problem definition and
> design of the solution on the list, is what "symlink" this refers
> to and how I am expected to use this feature.
>

I'll send something like this when I re-roll:

Follow symlinks inside the repository when requesting objects with extended SHA-1 expressions of the form tree-ish:path-in-tree. Instead of providing output about the link itself, provide output about the linked-to object. This option requires --batch or --batch-check. In the event of a symlink loop (or more than 40 symlinks in a symlink resolution chain), the file will be treated as missing. If a symlink points outside the tree-ish (e.g. a link to /foo or a root-level link to ../foo), the portion of the link which is outside the tree will be printed. Follow-symlinks will be silently turned off if <object> specifies an object in the index rather than one in the object database.

I could also provide some examples, if you think this would be useful.

> +If --follow-symlinks is used, and a symlink in the repository points
> > +outside the repository, then `cat-file` will ignore any custom

format

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> > +and print:
> > +
> > +------------
> > +symlink SP <size> LF <symlink> LF
> > +------------
> 
> A symlink contain LF, obviously, and we should use some quoting
> convention.  Perhaps quote_c_style() on a string that needs it is
> sufficient---most sane people do not put LF or literally '\' 'n' or
> '"' in their symbolic links, so the ugly output is not visible for
> them, and it is far better to be able to say "If you have funny
> characters in your symlinks, they will be quoted" than "If you have
> funny characters in your symlinks, you are SOL".
>

There is no need for quoting because <size> is sufficient to disambiguate the parsing (just as is the case for blobs, which might contain arbitrary characters).