Using "-" for "previous branch" failing with rebase

I recently learned that there are several places where git allows use of "-" to refer to the previous branch, e.g.

  git checkout -b dev
  # hack, hack
  git checkout master
  git merge -
  git checkout -

However, it doesn't seem to understand "-" in the context of a rebase:

  git checkout branch_a
  # hack
  git commit -a
  git checkout branch_b
  # hack
  git commit -a
  git rebase -         # I'd expect to rebase onto branch_a

but I get

  fatal: Needed a single revision
  invalid upstream -

Issuing

  git rebase branch_a

does exactly what I'd expect (as "git checkout -" puts me on "branch_a").

Is this just an interface inconsistency or is there a some technical reason this doesn't work (or, has it been addressed/fixed, and just not pulled into Debian Stable's 1.7.10.4 version of git)?

Thanks,

-tkc

Tim Chase <git@tim.thechases.com> writes:

It is merely that nobody thought "rebase" would benefit from such a short-hand, I think.

    Teach more commands that operate on branch names about "-"
    shorthand for "the branch we were previously on", like we did
    for "git merge -" sometime after we introduced "git checkout -"

has been sitting in my "leftover bits" list at

    http://git-blame.blogspot.com/p/leftover-bits.html

for quite some time.  Hint, hint...

On 2014-03-16 23:37, Junio C Hamano wrote:

Not sure if the "Hint, hint" was intended for me, as I'm not exactly a git hacker. I did find another place where I reached for it instinctively (now that I use it regularly with checkout/merge): git-diff.

  git checkout some_branch
  #hack
  git commit -m "..."
  git checkout other_branch
  # hmm...what's different between these branches?
  git diff -

which I would have expected to act something like

  git diff some_branch..other_branch

Just for the archives.

-tkc

(or possibly the reverse)

Tim Chase <git@tim.thechases.com> writes:

No. It is primarily a search-engine bait ;-) and is secondarily a hint to any aspiring Git hackers on the list.

In general, I am not very enthused to see the single letter "-" used where you name any commit object (like "diff"). It is a short-hand for the @{-1} notation that names the branch name, and it is OK in general to add support for it to the places where we expect a branch name and not just any commit object name (e.g. "checkout -"), but maybe it is just me who was heavily involved in the original design.