[PATCH 0/2] Detect empty or missing reflogs with `ref@{0}`

Hi,

this patch series addresses some shortcomings when parsing `ref@{n}` syntax via `read_ref_at()` when the reflog is missing or empty:

  - First, as reported by Yasushi, git-show-branch(1) would segfault
    because the function does not report when the 0th entry wasn't
    found.

  - Second, `ref@{0}` would fall back to return the object ID of ref
    itself in case the reflog is empty or missing. This behaviour is
    quite confusing and only works by chance.

The series addresses both of these issues by detecting and reporting the case where the reflog is empty or missing.

Patrick

Patrick Steinhardt (2):
  object-name: detect and report empty reflogs
  builtin/show-branch: detect empty reflogs

 builtin/show-branch.c          |  2 ++
 object-name.c                  | 10 ++++++----
 refs.c                         |  3 ++-
 t/t1506-rev-parse-diagnosis.sh |  8 ++++++++
 t/t1508-at-combinations.sh     | 29 +++++++++++++++++++++++++----
 t/t3202-show-branch.sh         | 25 +++++++++++++++++++++++++
 6 files changed, 68 insertions(+), 9 deletions(-)