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
rebase: fix for hgsubversion
5c25fe7fb1e broke something in the hgsubversion test path, causing it raise an
abort (Abort: nothing to merge) during a perfectly good rebase. I tracked it
down to this change. It's probably not hgsubversion related.
I suspect that using the same `wctx` from before the initial update causes
problems with the wctx's cached manifest property. I noticed we also sometimes
stick random gunk on the wctx object in other places (like in `copies.py`) so
it's probably best to reset it for now.
The line I added before was actually useless since we don't pass wctx to the
initial `merge.update`, so it defaults to `repo[None]`. So I just removed it.
Differential Revision: https://phab.mercurial-scm.org/D1679