git-submodule - possibly use branch name to describe a module

This changes the search logic for describing a submodule from: - annotated tag - any tag - tag on a subsequent commit - commit id to - annotated tag - any tag - tag on a subsequent commit - local or remote branch - commit id The change is describing with respect to a branch before falling back to the commit id. By itself, git-submodule will maintain submodules as headless checkouts without ever making a local branch. In general, such heads can always be described relative to the remote branch regardless of existence of tags, and so provides a better fallback summary than just the commit id. This requires inserting an extra describe step as --contains is incompatible with --all, but the latter can be used with --always to fall back to a commit ID. Also, --contains implies --tags, so the latter is not needed. Signed-off-by: Mark Levedahl <mlevedahl@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>