added afunction to check for the existence of MERGE_HEAD
added afunction to check for the existence of MERGE_HEAD

BugTesterTest/desktops,desktop/desktop,shiftkey/desktop,say25/desktop,BugTesterTest/desktops,kactus-io/kactus,kactus-io/kactus,j-f1/forked-desktop,artivilla/desktop,hjobrien/desktop,hjobrien/desktop,j-f1/forked-desktop,j-f1/forked-desktop,desktop/desktop,say25/desktop,BugTesterTest/desktops,gengjiawen/desktop,desktop/desktop,artivilla/desktop,gengjiawen/desktop,say25/desktop,hjobrien/desktop,artivilla/desktop,gengjiawen/desktop,BugTesterTest/desktops,desktop/desktop,shiftkey/desktop,kactus-io/kactus,shiftkey/desktop,artivilla/desktop,gengjiawen/desktop,hjobrien/desktop,say25/desktop,j-f1/forked-desktop,kactus-io/kactus,shiftkey/desktop