Consider a repository with branch master, with upstream origin/master.
If one is on master, and runs "git checkout @{u}" to get the upstream,
then git branch stops working. The reason is that we end up on a
detached HEAD, and git branch searches recent reflog entries to figure
out where the HEAD was detached from (wt-status.c:
wt_status_get_detached_from). Since @{u} is not a local branch, the
checkout is inserted into the reflog as "moving from master to @{u}"
rather than "moving from master to origin/master". This is because
setup_branch_path (checkout.c) only updates the branch name for local
branches, keeping the input name (here, "@{u}") otherwise. So, git
branch sees "@{u}", decides that we are detached from "@{u}", tries to
lookup "HEAD@{u}" and fails with "fatal: HEAD does not point to a
branch"
I assume that either the reflog entry should be amended to print
something more informative (moving from master to origin/master, or at
least master@{u}, or the SHA...), or the reflog search in
wt_status_get_detached_from should do something cleverer with relative
refs.
- Leszek
