Re: [GSoC][PATCH] submodule: port submodule subcommand 'add' from shell to C

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

Shourya Shukla <shouryashukla.oo@gmail.com> writes:

> 	if test -z "$force"
> 	then
> 		git ls-files --error-unmatch "$sm_path" > /dev/null 2>&1 &&
> 		die "$(eval_gettext "'\$sm_path' already exists in the index")"
> 	else
> 		git ls-files -s "$sm_path" | sane_grep -v "^160000" > /dev/null 2>&1 &&
> 		die "$(eval_gettext "'\$sm_path' already exists in the index and is not a submodule")"
> 	fi

Hmph.  So,

 - if we are not being 'force'd, we see if there is anything in the
   index for the path and error out, whether it is a gitlink or not.

 - if there is 'force' option, we see what the given path is in the
   index, and if it is already a gitlink, then die.  That sort of
   makes sense, as long as the remainder of the code deals with the
   path that is not a submodule in a sensible way.

> This is what I have done in C:
>
> 	if (!force) {
> 		if (is_directory(path) && submodule_from_path(the_repository, &null_oid, path))
> 			die(_("'%s' already exists in the index"), path);

The shell version would error out with anything in the index, so I'd
expect that a faithful conversion would not call is_directory() nor
submodule_from_path() at all---it would just look path up in the_index
and complains if anything is found.  For example, the quoted part in
the original above is what gives the error message when I do

	$ git submodule add ./Makefile
	'Makefile' already exists in the index.

I think.  And the above code won't trigger the "already exists" at
all because 'path' is not a directory.

> 	} else {
> 		int err;
> 		if (index_name_pos(&the_index, path, strlen(path)) >= 0 &&
> 		    !is_submodule_populated_gently(path, &err))
> 			die(_("'%s' already exists in the index and is not a "
> 			      "submodule"), path);

Likewise.  The above does much more than the original.

The original was checking if the found cache entry has 160000 mode
bit, so the second test would not be is_submodule_populated_gently()
but more like !S_ISGITLINK(ce->ce_mode)

Now it is a different question if the original is correct to begin
with ;-).  

> 	}
>
> Is this part correct? I am not very sure about this. This particular
> part is not covered in any test or test script, so, I do not have a
> solid method of knowing the correctness of this segment.
> Feedback and reviews are appreciated.