preliminary fixes for reftable support

these two commits to the reftable library prepare for making 2 tests in the test suite pass in my pending changes for reftable support.

This series was built against 'master'. It also has a fix for a fd leak (>= 0 vs > 0), which is part of my reftable-coverity fixes topic.

Han-Wen Nienhuys (3):
reftable: fix typo in header
reftable: signal overflow
reftable: support preset file mode for writing

 reftable/block.h           |  2 +-
 reftable/error.c           |  2 ++
 reftable/readwrite_test.c  | 35 +++++++++++++++++++++++++++++++++++
 reftable/reftable-error.h  |  4 ++++
 reftable/reftable-writer.h |  3 +++
 reftable/stack.c           | 30 ++++++++++++++++++++++++------
 reftable/stack_test.c      | 33 +++++++++++++++++++++++++++++----
 reftable/writer.c          |  3 +++
 8 files changed, 101 insertions(+), 11 deletions(-)

base-commit: fae76fe5da3df25d752f2251b7ccda3f62813aa9
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1164%2Fhanwen%2Freftable-features-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1164/hanwen/reftable-features-v1
Pull-Request: https://github.com/git/git/pull/1164

gitgitgadget