Re: [PATCH 1/1] builtin/checkout: simplify metadata initialization

> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
> 
> > When we call init_checkout_metadata in reset_tree, we want to pass the
> > object ID of the commit in question so that it can be passed to filters,
> > or if there is no commit, the tree.  We anticipated this latter case,
> > which can occur elsewhere in the checkout code, but it cannot occur
> > here, since reset_tree is called only (indirectly) via switch_branches,
> > which requires that we have a valid commit.  switch_branches dies if we
> > lack a name and cannot produce a commit from HEAD, and its caller dies
> > if we do have a branch name but still lack a commit pointer.
> >
> > Since we know we must always have a valid commit structure in this case,
> > let's remove the dead code paths and just refer to the commit structure.
> > This simplifies the code and makes it easier for the reader.
> 
> builtin/checkout.c::merge_working_tree() has these lines in its
> earlier part:
> 
> 	if (opts->new_orphan_branch && opts->orphan_from_empty_tree) {
> 		if (new_branch_info->commit)
> 			BUG("'switch --orphan' should never acc...");
> 		new_tree = parse_tree_indirect(the_hash_algo->empty_tree);
> 	} else
> 		new_tree = get_commit_tree(new_branch_info->commit);
> 	if (opts->discard_changes) {
> 		ret = reset_tree(new_tree, opts, 1, writeout_error, new_branch_info);
> 		if (ret)
> 			return ret;
> 	...
> 
> So, when orphan && orphan-from-empty are both set, we must not have
> commit, and then if discard is also there, we end up passing
> new_brnach_info that has NULL in its commit.