upgrade_chroot: create an upgrade script

cros_upgrade_chroot

+#!/bin/bash
+
+# Copyright (c) 2010 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.
+
+# Load common constants.  This should be the first executable line.
+# The path to common.sh should be relative to your script's location.
+. "$(dirname $0)/common.sh"
+
+# Script must be run inside the chroot
+restart_in_chroot_if_needed $*
+
+DEFINE_string version "" \
+  "Assume current chroot version is this."
+DEFINE_boolean force_latest "${FLAGS_false}" \
+  "Assume latest version and recreate the version file"
+DEFINE_boolean skipfirst "${FLAGS_false}" \
+  "Skip the first upgrade. This may be dangerous."
+
+FLAGS "$@" || exit 1
+
+VERSION_FILE=~/.version
+
+######################################################################
+
+# Latest version is the version of last upgrade.d file.
+# Name format is ${number}_${short_description}
+# Versions must be -n sorted, that is, the first continuous sequence
+# of numbers is what counts. 12_ is before 111_, etc.
+LATEST_VERSION=$(
+  ls "$(dirname $0)/upgrade.d" | grep "^[0-9]*_" | \
+  sort -n | tail -n 1 | cut -f1 -d'_'
+)
+CHROOT_VERSION=$(cat ${VERSION_FILE})
+# Check if it's a number.
+if ! [ "${CHROOT_VERSION}" -ge "0" ] &> /dev/null; then
+  error "Your chroot version file ${VERSION_FILE} is bogus: ${CHROOT_VERSION}"
+  exit 1
+fi
+
+if [ -n "${FLAGS_force_latest}" ]; then
+  echo "${LATEST_VERSION}" > "${VERSION_FILE}"
+  exit 0
+fi
+
+if [ -n "${FLAGS_skipfirst}" ]; then
+  if [ "${CHROOT_VERSION}" -lt "${LATEST_VERSION}" ]; then
+    CHROOT_VERSION=$(expr ${CHROOT_VERSION} + 1)
+  fi
+fi
+
+if [ -n "${FLAGS_version}" ]; then
+  # Check if it's a number.
+  if [ "${FLAGS_version}" -ge "0" ] &> /dev/null; then
+    CHROOT_VERSION="${FLAGS_version}"
+  else
+    error "Trying to force invalid version: ${FLAGS_version}"
+    exit 1
+  fi
+fi
+
+# default goes here
+if ! [ -f "${VERSION_FILE}" ]; then
+  warn "Warning: chroot of unknown version, assuming 0"
+  echo "0" > "${VERSION_FILE}"
+fi
+
+if [ "${LATEST_VERSION}" -gt "${CHROOT_VERSION}" ]; then
+  echo "Outdated chroot found"
+
+  pushd "$(dirname $0)/upgrade.d/" 1> /dev/null
+  for n in $(seq "$(expr ${CHROOT_VERSION} + 1)" "${LATEST_VERSION}"); do
+    # Deprecation check; Deprecation can be done by removing old upgrade
+    # scripts and causing too old chroots to have to start over.
+    # This also means that the scripts have to form a continuous sequence.
+    if ! [ -f ${n}_* ]; then
+      error "Fatal: Upgrade ${n} doesn't exist."
+      error "Your chroot is too old, you need to re-create it!"

[kliegs, 2010/09/24 22:31:49]

Why not just put the command here?  Save people the need to tab to the website
to reread the docs since (hopefully) chroot won't be run often.  Unless you're
worried that the command listed here may be obsolete by the time its needed?  

This isn't really a major point or something that should necessarily block this
CL.  But I've always viewed tools like this as making things as easy as possible
for the consumers of the script and giving explicit instructions here (even if
its not a common or expected case) makes their life easier.  Sure all these
changes could come later, but maintenance never happens as much as we'd like and
if the effort is similar better to do it right in the initial version.

+      exit 1
+    fi
+
+    info "Rollup $(echo ${n}_*)"
+
+    # Attempt the upgrade.
+    # NOTE: We source the upgrade scripts because:
+    # 1) We can impose set -something on them.
+    # 2) They can reuse local variables and functions (fe. from common.sh)
+    # A side effect is that the scripts have to be internally enclosed in
+    # a code block, otherwise simply running "exit" in any of them would
+    # terminate the master script, and there would be no way to pass the
+    # return value from them.
+    if ! source ${n}_*; then
+      error "Fatal: failed to upgrade ${n}!"
+      exit 1
+    fi
+    echo "${n}" > "${VERSION_FILE}"
+  done
+  popd 1> /dev/null
+fi