tree 674dfbfdeee336e2c5422bc9f99cabb82b4cf1d2
parent 66c78e0653a4e60c625b8400da31da0ba5bd1286
author Jeff King <peff@peff.net> 1763168298 +0000
committer Junio C Hamano <gitster@pobox.com> 1763270329 -0800

read-cache: drop submodule check from add_to_cache()

In add_to_cache(), we treat any directories as submodules, and complain
if we can't resolve their HEAD. This call to resolve_gitlink_ref() was
added by f937bc2f86 (add: error appropriately on repository with no
commits, 2019-04-09), with the goal of improving the error message for
empty repositories.

But we already resolve the submodule HEAD in index_path(), which is
where we find the actual oid we're going to use. Resolving it again here
introduces some downsides:

  1. It's more work, since we have to open up the submodule repository's
     files twice.

  2. There are call paths that get to index_path() without going through
     add_to_cache(). For instance, we'd want a similar informative
     message if "git diff empty" finds that it can't resolve the
     submodule's HEAD. (In theory we can also get there through
     update-index, but AFAICT it refuses to consider directories as
     submodules at all, and just complains about them).

  3. The resolution in index_path() catches more errors that we don't
     handle here. In particular, it will validate that the object format
     for the submodule matches that of the superproject. This isn't a
     bug, since our call in add_to_cache() throws away the oid it gets
     without looking at it. But it certainly caused confusion for me
     when looking at where the object-format check should go.

So instead of resolving the submodule HEAD in add_to_cache(), let's just
teach the call in index_path() to actually produce an error message
(which it already does for other cases). That's probably what f937bc2f86
should have done in the first place, and it gives us a single point of
resolution when adding a submodule to the index.

The resulting output is slightly more verbose, as we propagate the error
up the call stack, but I think that's OK (and again, matches many other
errors we get when indexing fails).

I've left the text of the error message as-is, though it is perhaps
overly specific.  There are many reasons that resolving the submodule
HEAD might fail, though outside of corruption or system errors it is
probably most likely that the submodule HEAD is simply on an unborn
branch.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>