A bit of test framework fixes with a few fixes to issues found by
valgrind.
source: <
20220512223218.237544-1-gitster@pobox.com>
* ab/valgrind-fixes:
commit-graph.c: don't assume that stat() succeeds
object-file: fix a unpack_loose_header() regression in
3b6a8db3b03
log test: skip a failing mkstemp() test under valgrind
tests: using custom GIT_EXEC_PATH breaks --valgrind tests