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
#require symlink
https://bz.mercurial-scm.org/1438
$ hg init
$ ln -s foo link
$ hg add link
$ hg ci -mbad link
$ hg rm link
$ hg ci -mok
$ hg diff -g -r 0:1 > bad.patch
$ hg up 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg import --no-commit bad.patch
applying bad.patch
$ hg status
R link
? bad.patch