Merge branch 'js/coverity-unchecked-returns-fix' into jch

A handful of code paths have been corrected to check return values
from functions like curl_easy_duphandle(), deflateInit(), lseek(),
dup(), and strbuf_getline_lf(), resolving several Coverity warnings
about unchecked returns.

* js/coverity-unchecked-returns-fix:
  bisect: handle dup() failure when redirecting stdout
  bisect: check get_terms return at all call sites
  bisect: check strbuf_getline_lf return when reading terms
  transport-helper: warn when export-marks file cannot be finalized
  transport-helper: check dup() return in get_exporter
  compat/pread: check initial lseek for errors
  last-modified: handle repo_parse_commit() failures
  reftable tests: check reftable_table_init_ref_iterator() return
  reftable/block: check deflateInit() return value
  config: propagate launch_editor() failure in show_editor()
  http: die on curl_easy_duphandle failure in get_active_slot

diff --cc builtin/bisect.c
Simple merge

diff --cc builtin/config.c
Simple merge

diff --cc http.c
Simple merge

diff --cc reftable/block.c
Simple merge

diff --cc t/unit-tests/u-reftable-table.c
Simple merge

diff --cc transport-helper.c
Simple merge