[PATCH v2 0/1] Run pipeline command in subshell in sh mode

["brian m. carlson" <sandals@xxxxxxxxxxxxxxxxxxxx>]

POSIX sh implementations run each command in a pipeline in a subshell,
although zsh (and AT&T ksh) do not: instead, they run the final command
in the main shell.  This leads to very different behavior when the final
command is a shell function which modifies variables.

zsh is starting to be used in some cases as /bin/sh, such as on macOS
Catalina.  Consequently, it makes sense to emulate the POSIX behavior as
much as possible when emulating sh, since that's the least surprising
behavior.  This patch does exactly that.

With this patch, using "zsh --emulate sh" passes the Git testsuite.  I
expect that it will also be fully functional as /bin/sh on Debian,
although I have not tested.

This patch was sent before, but didn't get picked up.  In hopes of
aiding reviewers, I've resent it with a significantly expanded commit
message so that it is easier to reason about.

I'm not subscribed to the list, so please CC me if you have questions or
comments.

brian m. carlson (1):
  exec: run final pipeline command in a subshell in sh mode

 Src/exec.c           | 10 ++++++----
 Test/B07emulate.ztst | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 4 deletions(-)