Re: [PATCH] difftool: handle changing symlinks in dir-diff mode

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Junio,

On Mon, 13 Mar 2017, Junio C Hamano wrote:

> David Aguilar <davvid@gmail.com> writes:
> 
> > +static int create_symlink_file(struct cache_entry* ce, struct checkout* state)
> 
> Asterisk sticks to variable, not type.

If only we had tools to format the code so that authors as well as
reviewers could concentrate on essential parts of the patches :-)

> > +	 * into the checkout state's path.
> > +	 */
> > +	struct strbuf path = STRBUF_INIT;
> > +	struct strbuf link = STRBUF_INIT;
> > +
> > +	int ok = 0;
> > +
> > +	if (strbuf_readlink(&link, ce->name, ce_namelen(ce)) == 0) {
> > +		strbuf_add(&path, state->base_dir, state->base_dir_len);
> > +		strbuf_add(&path, ce->name, ce_namelen(ce));
> > +
> > +		write_file_buf(path.buf, link.buf, link.len);
> 
> This does "write content into symlink stand-in file", but why?

From the commit message:

	> Detect the null object ID for symlinks in dir-diff so that
	> difftool can prepare temporary files that matches how git
	> handles symlinks.

The obvious connection: when core.symlinks = false, Git already falls back
to writing plain files with the link target as contents. This function
does the same, for the same motivation: it is the best we can do in this
case.

> Also, I am not sure if strbuf_readlink() can unconditionally used
> here.  On a filesystem without symbolic link, the working tree
> entity that corresponds to the ce that represents a symlink is a
> stand-in regular file, so shouldn't we be opening it as a regular
> file and reading its contents in that case?

I think you are right, we cannot simply call strbuf_readlink(), we would
have to check the core_symlinks variable to maybe read the file contents
instead.

But then, it may not be appropriate to read the worktree to begin with...
see my reply to the patch that I will send out in a couple of minutes.

Ciao,
Johannes