[PATCH 0/2] grep: tolerate NULL argument to free_grep_expr()

This short series demonstrates and fixes a bug whereby a NULL `struct grep_expr*` argument (such as when running `git log --invert-grep` without a `--grep` argument) could cause us to segfault when trying to dereference that argument.

An alternative approach is to disallow `--invert-grep` without a `--grep` argument. But a more user-friendly approach is to permit this combination by pretending as if neither argument was given. This patch series takes the latter approach by teaching free_grep_expr() that passing a NULL argument should result in a noop, not a segfault.

Taylor Blau (2):
  t4202: demonstrate `git log --invert-grep` segfault
  grep.c: tolerate NULL grep_expr in free_pattern_expr()

 grep.c         | 5 +++--
 t/t4202-log.sh | 6 ++++++
 2 files changed, 9 insertions(+), 2 deletions(-)