Without quorum for the default branch, the remote helper would report
an error, suggesting that the patch was not updated, while,
inconsistently, actually updating the ref in storage without creating
a new revision.
$ git push …
To rad://z…5/z…z
…
! [remote rejected] 612… -> patches/a77… (…)
error: failed to push some refs to 'rad://z…5/z…z'
…
$ git ls-remote rad://z…5/z…z
612… refs/heads/patches/a77…
This is very confusing.
Fix this by using a temporary reference name that is different from the
reference name that the patch would use, implementing cleanup via
`Drop`.
While at it, also move the logic into `patch_base` and share it
between `patch_open` and `patch_update`. Computation of the canonical
head via `stored.canonical_head` is moved to a branch that is only
taken if the user did not specify a base explicitly. This allows to
update patches even when there is no quorum for the default branch.
9bb136105c