That's a bug. Emacs' process has the wrong pgid when its parent isn't an interactive shell. Here's a workaround for the same problem using Git. I would hope you can configure Mercurial similarly.

Emacs C-g Kills `git commit` On Mac OS X

2012-02-22

Workaround: Invoke Emacs via an interactive Bash shell.

emacs.sh:


    #! /bin/bash -i

    emacs "$@"

In a shell:


    git config --global core.editor emacs.sh

See also:

Matt McClure

http://matthewlmcclure.com

http://www.mapmyfitness.com/profile/matthewlmcclure

On May 21, 2012, at 9:54 AM, Roy Smith <roy@panix.com> wrote:

I'm running:

GNU Emacs 22.1.1
OSX-10.6.8
Mercurial Distributed SCM (version 1.6.4+20101001)

If I do "hg commit", emacs is run as I would expect, but if I type a Control-G, I get an "interrupted!" message, and emacs quits (leaving the terminal modes unrestored).

Running ps shows that the command being executed is:

emacs -nw /var/folders/p5/p5Gj6NRtF-yAXT+X0YVgJU+++TM/-Tmp-/hg-editor-wQEeGG.txt

If I run that manually, I get normal operation. I assume there's something funky about the environment in which emacs is being executed, but I can't figure out what that might be. Any ideas?

It doesn't seem to be related to the buffer; I get the same problem in other buffers. M-X make command summary shows, for both the normal and broken situations:

C-g keyboard-quit <JISX0208> self-insert-command

--
Roy Smith
roy@panix.com