extdata: abort if external command exits with non-zero status (BC) Per the last discussion, this is more reliable and consistent way than suppressing an error. For grep, erroring out might be inconvenient, but for curl, non-zero exit status should be detected. The latter wouldn't be possible if non-zero status is ignored. https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-October/105727.html