diff --git a/emacs-build.sh b/emacs-build.sh
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+#!/bin/bash
+# Copyright 2020 Juan Jose Garcia-Ripoll
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+#
+########################################
+#
+# EMACS-BUILD
+#
+# Standalone script to build Emacs from a running copy of Mingw64. It immitates
+# the steps that Emacs developers can take to build the standard distributions.
+# See write_help below for all options.
+#
+
+function write_help () {
+    cat <<EOF
+Usage:
+
+   ./emacs-build.sh [-64] [-32] [--clone] [--build] [--deps] [--without-X] [--with-X]
+
+Actions:
+
+   --clone       Download Savannah's git repository for Emacs
+   --ensure      Ensure that required packages are installed
+   --build       Configure and build Emacs from sources
+   --deps        Create a ZIP file with all the Mingw64/32 dependencies
+   --package     Package an Emacs previously built with the --build option
+
+   Multiple actions can be selected. The default is to run them all in a logical
+   order: clone, ensure, build, deps and package.
+
+Options:
+   -64           Prepare or build for Mingw64 (default)
+   -32           Prepare or build for Mingw32
+   --slim        Remove Cairo, SVG and TIFF support for a slimmer build
+                 Remove also documentation files and other support files
+                 from the dependencies file
+   --with-X      Add requested feature in the dependencies and build
+   --without-X   Remove requested feature in the dependencies and build
+
+   X is any of the known features for emacs in Windows/Mingw:
+     $all_features
+EOF
+
+}
+
+function errcho ()
+{
+    echo $@ >&2
+}
+
+
+function full_dependency_list ()
+{
+    # Given a list of packages, print a list of all dependencies
+    #
+    # Input
+    #  $1 = list of packages without dependencies
+    #
+    # Packages we do not want to distribute (spurious dependencies)
+    local skip_pkgs="glib2"
+    # Packages that have to be replaced by others for distribution
+    local munge_pgks="
+        s,$mingw_prefix-libwinpthread,$mingw_prefix-libwinpthread-git,g;
+        s,$mingw_prefix-libtre,$mingw_prefix-libtre-git,g;"
+
+    local packages=`for i in $packages; do echo $mingw_prefix-$i; done`
+    local skip_pkgs=`for p in $skip_pkgs; do echo s,$mingw_prefix-$p,,g; done`
+
+    local oldpackages=""
+    local dependencies=""
+    while test "$oldpackages" != "$packages" ; do
+        oldpackages="$packages"
+        dependencies=`pacman -Qii $oldpackages | grep Depends | sed -e 's,>=[^ ]*,,g;s,Depends[^:]*:,,g;s,None,,g;' -e "$skip_pkgs" -e "$munge_pgks"`
+        packages=`echo $oldpackages $dependencies | sed -e 's, ,\n,g' | sort | uniq`
+    done
+    echo $packages
+}
+
+function emacs_dependencies ()
+{
+    # Print the list of all mingw/msys packages required for running emacs with
+    # the selected features. Cache the result value.
+    #
+    if test -z "$emacs_dependencies"; then
+        errcho Inspecting required packages for build features
+        errcho   $features
+        local feature_selector=`echo $features | sed -e 's, ,|,g'`
+        local packages=`feature_list | grep -E "$feature_selector" | cut -d ' ' -f 2-`
+        emacs_dependencies=`full_dependency_list $packages`
+        errcho Total packages required:
+        errcho   `echo $emacs_dependencies | sed -e 's, ,\n,g' -`
+    fi
+    echo $emacs_dependencies
+}
+
+function prepare_source_dir ()
+{
+    if test -d "$source_dir"; then
+        if test -f "$source_dir/configure"; then
+            echo Configure script exists. Nothing to do in source directory $source_dir
+            echo
+            return 0
+        fi
+        cd "$source_dir" && ./autogen.sh && return 0
+        echo Unable to prepare source directory. Autoreconf failed.
+    else
+        echo Source directory $source_dir missing
+        echo Run script with --clone first
+        echo
+    fi
+    return -1
+}
+
+function prepare_build_dir ()
+{
+    if test -d "$build_dir"; then
+        if test -f "$build_dir/config.log"; then
+            rm -rf "$build_dir/*"
+        else
+            echo Cannot rebuild on existing directory $build_dir
+            return -1
+        fi
+    else
+        mkdir -p "$build_dir"
+    fi
+}
+
+function configure_build_dir ()
+{
+    cd "$build_dir"
+    options="--without-compress-install --without-dbus"
+    for f in $all_features; do
+        if echo $features | grep f > /dev/null; then
+            options="--with-$f $options"
+        else
+            options="--without-$f $options"
+        fi
+    done
+    echo Configuring Emacs with options
+    echo   $options
+    if "$source_dir/configure" "--prefix=$install_dir" $options >$log_file 2>&1; then
+        echo Emacs configured
+    else
+        echo Configuration failed
+        return -1
+    fi
+}
+
+function action0_clone ()
+{
+    # Download the Emacs source files using Git.
+    #
+    if which git >/dev/null 2>&1; then
+        echo Found git, nothing to install.
+    else
+        echo Git is not found, installing it.
+        pacman -S --noconfirm git
+    fi
+    pushd . >/dev/null
+    local error
+    if test -d "$source_dir"; then
+        echo Updating repository
+        cd "$source_dir"
+        git pull && git reset --hard && git checkout
+        error=$?
+        if test $? != 0; then
+            echo Source repository update failed.
+        fi
+    else
+        echo Cloning Emacs repository from Savannah at $emacs_repo.
+        git clone --depth 1 -b $branch "$emacs_repo" "$source_dir" && \
+            cd "$source_dir" && git config pull.rebase false
+        error=$?
+        if test $? != 0; then
+            echo Git clone failed. Deleting source directory.
+            rm -rf "$source_dir"
+        fi
+    fi
+    #
+    # If there was a 'configure' script, remove it, to force running autoreconf
+    # again before builds.
+    rm -f "$source_dir/configure"
+    popd >/dev/null
+    return $?
+}
+
+function action1_ensure_packages ()
+{
+    # Collect the list of packages required for running Emacs, and ensure they
+    # have been installed.
+    #
+    echo Ensuring packages are installed
+    if pacman -Qi `emacs_dependencies` >/dev/null; then
+        echo All packages are installed.
+    else
+        echo Some packages are missing. Installing them with pacman.
+        pacman -S --noconfirm -q `emacs_dependencies`
+    fi
+}
+
+function action2_build ()
+{
+    if prepare_source_dir && prepare_build_dir && configure_build_dir; then
+        echo Building Emacs in directory $build_dir
+        echo Log file is saved into $log_file
+        if make -j 4 -C $build_dir $build_dir >>$log_file 2>&1; then
+            echo Installing Emacs into directory $install_dir
+            if make -j 4 -C $build_dir install >>$log_file 2>&1; then
+                echo Process succeeded
+                return 0
+            fi
+        fi
+    fi
+    echo Configuration and build process failed
+    echo Please check log file $log_file
+    return -1
+}
+
+function action3_package_deps ()
+{
+    # Collect the list of packages required for running Emacs, gather the files
+    # from those packages and compress them into $emacs_depsfile
+    #
+    rm -f "$emacs_depsfile"
+    mkdir -p `dirname "$emacs_depsfile"`
+    cd $mingw_dir
+    pacman -Ql `emacs_dependencies` | cut -d ' ' -f 2 | sort | uniq \
+        | sed "s,^$mingw_dir,,g" | dependency_filter | xargs zip -9 "$emacs_depsfile"
+}
+
+function action4_package ()
+{
+    # Package a prebuilt emacs with and without the required dependencies, ready
+    # for distribution.
+    #
+    if test ! -f $emacs_depsfile; then
+        echo Missing dependency file $emacs_depsfile. Run with --deps first.
+    fi
+    rm -f "$install_dir/bin/emacs-*.exe"
+    strip "$install_dir/bin/*.exe" "$install_dir/libexec/emacs/*/*/*.exe"
+    rm -f "$emacs_nodepsfile"
+    mkdir -p `dirname "$emacs_nodepsfile"`
+    cd "$install_dir"
+    if zip -9vr "$emacs_nodepsfile" *; then
+        echo Built $emacs_nodepsfile; echo
+    else
+        echo Failed to compress distribution file $emacs_nodepsfile; echo
+        return -1
+    fi
+    cp $emacs_depsfile $emacs_distfile
+    cd "$install_dir"
+    if zip -9vr "$emacs_distfile" *; then
+        echo Built $emacs_distfile; echo
+    else
+        echo Failed to compress distribution file $emacs_distfile; echo
+        return -1
+    fi
+}
+
+function feature_list () {
+    cat <<EOF
+xpm xpm-nox
+jpeg libjpeg-turbo
+tiff libtiff
+gif giflib
+png libpng
+rsvg librsvg
+cairo cairo
+harfbuzz harfbuzz
+json jansson
+lcms2 lcms2
+xml2 libxml2
+gnutls gnutls
+zlib zlib
+EOF
+
+}
+
+function delete_feature () {
+    features=`echo $features | sed -e "s,$1,,"`
+}
+
+function add_feature () {
+    features=`echo $features $1 | sort | uniq`
+}
+
+function dependency_filter () {
+    if test -z "$dependency_exclusions"; then
+        cat -
+    else
+        grep -E -v "^(`echo $slim_exclusions | sed 's, ,|,g'`)" -
+    fi
+}
+
+slim_exclusions="
+include/
+lib/.*.a
+lib/cmake
+lib/gettext/intl
+lib/pkgconfig
+lib/python3.8
+share/aclocal
+share/doc/gettext
+share/doc/libasprintf
+share/doc/libiconv
+share/doc/libjpeg-turbo
+share/doc/libunistring
+share/doc/libxml2
+share/doc/mpfr
+share/doc/tiff
+share/doc/xz
+share/gettext/intl
+share/gtk-doc/html/libxml2
+share/man/man3
+share/man/man5
+"
+dependency_exclusions=""
+all_features=`feature_list | cut -f 1 -d ' '`
+features="$all_features"
+branches=""
+architectures=""
+actions=""
+while test -n "$*"; do
+    case $1 in
+        -64) architectures="$architectures x86_64";;
+        -32) architectures="$architectures i686";;
+        --branch) shift; branches="$branches $1";;
+        --without-*) delete_feature `echo $1 | sed -e 's,--without-,,'`;;
+        --with-*) add_feature `echo $1 | sed -e 's,--without-,,'`;;
+        --slim)
+            delete_feature cairo
+            delete_feature rsvg
+            delete_feature tiff
+            dependency_exclusions="$slim_exclusions"
+            ;;
+        --clone) actions="$actions action0_clone";;
+        --ensure) actions="$actions action1_ensure_packages";;
+        --build) actions="$actions action2_build";;
+        --deps) actions="$actions action3_package_deps";;
+        --package) actions="$actions action4_package";;
+        --help) write_help; exit 0;;
+    esac
+    shift
+done
+if test -z $architectures; then
+    architectures="x86_64"
+fi
+if test -z "$branches"; then
+    branches="emacs-27"
+fi
+actions=`for a in $actions; do echo $a; done|sort`
+if test -z "$actions"; then
+    actions="action0_clone action1_ensure_packages action2_build action3_package_deps action4_package"
+fi
+features=`for f in $features; do echo $f; done | sort | uniq`
+
+emacs_repo=https://git.savannah.gnu.org/git/emacs.git
+for branch in $branches; do
+    for architecture in $architectures; do
+        mingw_prefix="mingw-w64-x86_64"
+        mingw_dir="/mingw64/"
+        if test $architecture = i686; then
+            mingw_prefix="mingw-w64-i686"
+            mignw_dir="/mingw32/"
+        fi
+        emacs_nodepsfile="`pwd`/zips/emacs-${branch}-${architecture}-nodeps.zip"
+        emacs_depsfile="`pwd`/zips/emacs-${branch}-${architecture}-deps.zip"
+        emacs_distfile="`pwd`/zips/emacs-${branch}-${architecture}-full.zip"
+        emacs_dependencies=""
+        for action in $actions; do
+            source_dir="`pwd`/git/$branch"
+            build_dir="`pwd`/build/$branch-$architecture"
+            install_dir="`pwd`/pkg/$branch-$architecture"
+            log_file="${build_dir}.log"
+            if $action ; then
+                echo Action $action succeeded.
+            else
+                echo Action $action failed.
+                echo Aborting builds for branch $branch and architecture $architecture
+                break
+            fi
+        done
+    done
+done