Re: Bug with "git mv" and submodules, and with "git submodule add something --force"

[Junio C Hamano <gitster@pobox.com>]

Jonathan Nieder <jrnieder@gmail.com> writes:

> Stefan Beller wrote:
>
>> Maybe for now we can do with just an update of the documentation/bugs
>> section and say we cannot move files in and out of submodules?
>
> I think we have some existing logic to prevent "git add"-ing a file
> within a submodule to the superproject, for example.

There is die_path_inside_submodule() that sanity-checks the pathspec
and rejects.  But I think that is done primarily to give an error
message and not strictly necesary for correctness.

The real safety of "git add" is its call to dir.c::fill_directory();
it collects untracked paths that match the pathspec so that they can
be added as new paths, but because it won't cross the module
boundary, you won't get such a path in the index to begin with.

> So "git mv" should learn the same trick.  And perhaps the trick needs
> to be moved down a layer (e.g. into the index API).  Hints?

You would want to be able to remove a submodule and replace it with
a directory, but you can probably do it in two steps, i.e.

	git reset --hard
	git rm --cached sha1collisiondetection
	echo Now a regular dir >sha1collisiondetection/READ.ME
	find sha1collisiondetection ! -type d -print0 | 
	git update-index --add --stdin -z

So from that point of view, forbidding (starting from the same state
of our project) this sequence:

	git reset --hard
	echo Now a regular dir >sha1collisiondetection/READ.ME
	find sha1collisiondetection ! -type d -print0 | 
	git update-index --add --remove --stdin -z

that would nuke the submodule and replace it with a directory within
which there are files would be OK.  Making the latter's default
rejection overridable with ADD_CACHE_OK_TO_REPLACE would also be
fine.