Fix enter_chroot.sh so that it can be run from a cwd that is not in a git repository

enter_chroot.sh

 #!/bin/bash
 
 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to enter the chroot environment
 
 # Load common constants.  This should be the first executable line.
 # The path to common.sh should be relative to your script's location.
@@ skipping 254 matching lines @@
 # the wrong version, which would mess up the .git directories.
 #
 # Note that this fixes $CHROMEOS_REVISION at the time the chroot is
 # entered.  That's ok for the main use case of automated builds,
 # which pass each command line into a separate call to enter_chroot
 # so always have up-to-date info.  For developer builds, there may not
 # be a single revision, since the developer may have
 # hand-sync'd some subdirs and edited files in others.
 # In that case, check against origin/HEAD and mark** revision.
 # Use git:8 chars of sha1
-REVISION=$(git rev-parse --short=8 HEAD)
+REVISION=$(cd ${FLAGS_trunk}/src/scripts ; git rev-parse --short=8 HEAD)
 CHROOT_PASSTHRU="CHROMEOS_REVISION=$REVISION BUILDBOT_BUILD=$FLAGS_build_number CHROMEOS_OFFICIAL=$CHROMEOS_OFFICIAL"
 if [ -d "$HOME/.subversion" ]; then
   # Bind mounting .subversion into chroot
   info "mounting ~/.subversion into chroot"
   MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}/home/${USER}/.subversion")"
   if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]; then
     mkdir -p "$MOUNTED_PATH"
     sudo mount --bind "$HOME/.subversion" "$MOUNTED_PATH" || \
       die "Could not mount $MOUNTED_PATH"
   fi
 fi
 
 # Configure committer username and email in chroot .gitconfig
 git config -f ${FLAGS_chroot}/home/${USER}/.gitconfig --replace-all user.name \
   "$(cd /tmp; git var GIT_COMMITTER_IDENT | sed -e 's/ *<.*//')"
 git config -f ${FLAGS_chroot}/home/${USER}/.gitconfig --replace-all user.email \
   "$(cd /tmp; git var GIT_COMMITTER_IDENT | sed -e 's/.*<\([^>]*\)>.*/\1/')"
 
 # Run command or interactive shell.  Also include the non-chrooted path to
 # the source trunk for scripts that may need to print it (e.g.
 # build_image.sh).
 sudo chroot "$FLAGS_chroot" sudo -i -u $USER $CHROOT_PASSTHRU \
   EXTERNAL_TRUNK_PATH="${FLAGS_trunk}" LANG=C SSH_AGENT_PID="${SSH_AGENT_PID}" \
   SSH_AUTH_SOCK="${SSH_AUTH_SOCK}" -- "$@"
 
 # Remove trap and explicitly unmount
 trap - EXIT
 teardown_env