patchgit-submodule - possibly use remote branch to describe a module

Absent user intervention, git-submodule will maintain submodules as headless checkouts of remote branches: such checkouts cannot be described with reference to any local branch. So, allow describing the submodule using remote branches before falling back on just using the commit id.

Signed-off-by: Mark Levedahl <mlevedahl@gmail.com>
---
 git-submodule.sh |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

Mark Levedahl <mlevedahl@gmail.com> writes:

I think the new fallback sequence makes sense, but your explanation made sense for me only after reading it two and half times.

 - The original sequence ended with "--contains --always" which always
   succeeded but with an abbrevated object name.  You removed --always
   from it so that you can add a better last-ditch effort that uses remote
   references.

   Side note.  Removal of --tags from it is not justified in your log
   message.  It is sort of obvious if you think about it, though...

 - The new one at the end uses --all because the HEAD is likely to be
   describable with remote references, and without --all remote reference
   namespace is not searched for a match.

Junio C Hamano wrote:

So, would you like for me to attempt a better log message?

Mark

This changes the search logic for describing a submodule from:
- local branch
- tag
- tag on a later commit
- commit id

to

- local branch
- tag
- tag on a subsequent commit
- remote branch
- commit id

The change is describing with respect to a remote 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 cannot be described relative to a local branch but can always be described relative to the remote branch.

This requires two describe steps in place of one: the first with "--contains" (and no "--tags" as that is implied by "--contains"), and a new final step having "--all --always". The split is needed as "--contains" is incompatible with "--all".

Signed-off-by: Mark Levedahl <mlevedahl@gmail.com>
---
 git-submodule.sh |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

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>
---
One more try - I mistakenly thought bare describe allowed
local branches, not just tags, so the logic IS different.W Oops.

 git-submodule.sh |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)