Re: [PATCH 1/2] update-ref: Allow creation of multiple transactions

On Thu, Nov 05, 2020 at 02:29:01PM -0500, Jeff King wrote:

On Wed, Nov 04, 2020 at 03:57:17PM +0100, Patrick Steinhardt wrote:

quoted

While git-update-ref has recently grown commands which allow interactive
control of transactions in e48cf33b61 (update-ref: implement interactive
transaction handling, 2020-04-02), it is not yet possible to create
multiple transactions in a single session. To do so, one currently still
needs to invoke the executable multiple times.

This commit addresses this shortcoming by allowing the "start" command
to create a new transaction if the current transaction has already been
either committed or aborted.

Thanks for working on this. The amount of change needed is indeed quite
pleasant.

quoted

diff --git a/Documentation/git-update-ref.txt b/Documentation/git-update-ref.txt
index d401234b03..48b6683071 100644
--- a/Documentation/git-update-ref.txt
+++ b/Documentation/git-update-ref.txt

@@ -125,7 +125,8 @@ option::
 start::
 	Start a transaction. In contrast to a non-transactional session, a
 	transaction will automatically abort if the session ends without an
-	explicit commit.
+	explicit commit. This command may create a new empty transaction when
+	the current one has been committed or aborted already.

Reading this made me wonder what would happen if we send a "start" when
the current one _hasn't_ been committed or aborted. I.e., what does:

  git update-ref --stdin <<EOF
  start
  create refs/heads/foo ...
  start
  commit
  EOF

do? It turns out that the second start is ignored totally (and the
commit does indeed update foo). I wonder if we ought to complain about
it. But that is completely orthogonal to your patch. The behavior is the
same before and after.

Agreed, that's a case where we should raise an error. Doing nothing
without any indication is a bad way of handling it.

Patrick