util: adjust hgexecutable() to handle frozen Mercurial on OS X sys.executable is "$appbundle/Contents/MacOS/python" when Mercurial is bundled in a frozen app bundle on OS X, so that isn't appropriate. It appears that this was only visible for things launched via util.system(), like external hooks, where $HG was set wrong. It appears that Mercurial also uses 'sys.modules['__main__'].__file__' (here) and 'sys.argv[0]' (in platform.gethgcmd()) to figure out the command to spawn. In both cases, this points to "$appbundle/Contents/Resources/hg", which invokes the system python since "/usr/bin/env python" is on the shebang line. On my system with a screwed up python install, I get an error importing the os module if this script is invoked. We could take the dirname of sys.executable and join 'hg' instead of this if we want to be paranoid, but py2app boostrap is setting the environment variable since 0.1.6 (current version is 0.9), so it seems safe and we might as well use it.