comint-insert-previous-argument doesn't detect and ignore trailing &

This function is invoked in shell-mode by the user, and is meant to
emulate what M-. does in zsh and bash: it inserts an argument from a
previous command.  Neither zsh nor bash treat a trailing & specially:
M-. simply inserts it if it is encountered.  Emacs DID have extra
logic to detect and discard trailing &, but this logic was buggy, and
a && anywhere in the sequence would confuse it.  This patch simply
removes that logic to fix the bug and to emulate zsh and bash more
closely

* lisp/comint.el (comint-insert-previous-argument): don't detect and
  ignore trailing &
  (Bug#25271)
* etc/NEWS: Document this.

1 files changed, 5 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 8bf1da470fc..87c3950b1e3 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -191,6 +191,11 @@ It now treats the optional 2nd argument to mean that the URL should be
 shown in the currently selected window.
 
 ** Comint
+*** 'comint-insert-previous-argument' no longer interprets &.
+This worked strangely in shell-mode in the presence of &&.  And omitting this
+logic makes sense since 'comint-insert-previous-argument' exists to emulate M-.
+in bash and zsh, and neither of those treat & specially.
+
 *** 'comint-insert-previous-argument' knows how to count args
 from the beginning or from the end.  This is useful because
 'comint-insert-previous-argument' exists to emulate M-. in bash and zsh; and