beesh: Add --fakeroot to fake root only for install and packaging

DEPENDENCIES

@@ -27,4 +27,8 @@ gzip, bzip2, xz, ..:
 man:
   to read our minimalistic manpages 8)
 
+fakeroot:
+  only for beesh --fakeroot, which runs the install and packaging
+  steps under fakeroot
+
 to be continued - please let us know if you find additional dependencies.

src/beesh.sh.in

@@ -111,6 +111,8 @@ function show_help() {
 	    -h, --help             display this help
 	    --no-archive-build     do not archive the build directory
 	    --check                run mee_check, mee_check_pre and mee_check_post
+	    --fakeroot             run only the install and packaging steps
+	                           under fakeroot instead of all of beesh
 
 	EOF
 }
@@ -705,6 +707,74 @@ function bee_archivebuild() {
         --transform="s,^${BEE_BEEDIR},${PKGALLPKG}/files,"
 }
 
+#### bee_fakeroot_start() #####################################################
+
+# Under fakeroot, the stat, chmod and chown calls of every process go through
+# the one faked daemon, which slows down file-heavy builds a lot. With
+# --fakeroot, only the steps that need the files in ${D} to look owned by root
+# run under it: install, crosscheck and packaging.
+#
+# Starting faked only now also keeps its database clean: files deleted by the
+# build outside of fakeroot would leave stale ownership records behind, which
+# a new file reusing the inode inherits.
+#
+# fakeroot keeps faked running only as long as its command, so the command
+# reports the environment to use and then waits until its standard input is
+# closed, by bee_fakeroot_stop() or by beesh exiting.
+function bee_fakeroot_start() {
+    local key preload library_path v
+
+    [ "${OPT_FAKEROOT}" = "yes" ] || return 0
+
+    if [ -n "${FAKEROOTKEY}" ] ; then
+        print_info "already running under fakeroot (FAKEROOTKEY=${FAKEROOTKEY})"
+        return 0
+    fi
+
+    bee_fakeroot_saved_env=()
+    for v in LD_PRELOAD LD_LIBRARY_PATH ; do
+        if [ -n "${!v+set}" ] ; then
+            bee_fakeroot_saved_env+=( "${v}=${!v}" )
+        fi
+    done
+
+    coproc BEE_FAKEROOT {
+        fakeroot -- sh -c 'printf "%s\n" "${FAKEROOTKEY}" "${LD_PRELOAD}" "${LD_LIBRARY_PATH}"; exec cat > /dev/null'
+    }
+    bee_fakeroot_pid=${BEE_FAKEROOT_PID}
+
+    if ! { read -r key && read -r preload && read -r library_path ; } <&"${BEE_FAKEROOT[0]}" \
+        || [ -z "${key}" ] ; then
+        print_error "ERROR: cannot start fakeroot"
+        exit 1
+    fi
+
+    print_info "starting fakeroot (FAKEROOTKEY=${key})"
+
+    export FAKEROOTKEY=${key}
+    export LD_PRELOAD=${preload}
+    export LD_LIBRARY_PATH=${library_path}
+}
+
+#### bee_fakeroot_stop() ######################################################
+
+function bee_fakeroot_stop() {
+    local e
+
+    [ -n "${bee_fakeroot_pid}" ] || return 0
+
+    print_info "stopping fakeroot"
+
+    unset FAKEROOTKEY LD_PRELOAD LD_LIBRARY_PATH
+    for e in "${bee_fakeroot_saved_env[@]}" ; do
+        export "${e}"
+    done
+
+    exec {BEE_FAKEROOT[1]}>&-
+    wait "${bee_fakeroot_pid}"
+    unset bee_fakeroot_pid
+}
+
 function load_buildmagic() {
     local oIFS=${IFS}
     local IFS=":${IFS}"
@@ -870,6 +940,7 @@ OPTIONS=$("${BEE_BINDIR}/beegetopt" --name beesh \
                  --option no-archive-build \
                  --option ignore-issue \
                  --option check \
+                 --option fakeroot \
                  -- "$@")
 
 if [ $? != 0 ] ; then
@@ -884,6 +955,7 @@ eval set -- "${OPTIONS}"
 : ${OPT_CHECK:="no"}
 : ${OPT_ARCHIVE_BUILD:="yes"}
 : ${OPT_IGNORE_ISSUE:="no"}
+: ${OPT_FAKEROOT:="no"}
 
 while true ; do
     case "$1" in
@@ -925,6 +997,10 @@ while true ; do
             OPT_CHECK="yes"
             shift
             ;;
+        --fakeroot)
+            OPT_FAKEROOT="yes"
+            shift
+            ;;
         --debug)
             DEBUG=$2
             shift 2
@@ -940,6 +1016,14 @@ while true ; do
     esac
 done
 
+# Find out now, not after a build of hours, that the install step cannot run.
+if [ "${OPT_FAKEROOT}" = "yes" -a -z "${FAKEROOTKEY}" ] ; then
+    if ! fakeroot -- true ; then
+        print_error "ERROR: --fakeroot needs a working fakeroot"
+        exit 1
+    fi
+fi
+
 config_init
 
 echo -e "${COLOR_CYAN}BEE v${BEE_VERSION} 2009-2016"
@@ -1093,6 +1177,8 @@ if [ "${OPT_CHECK}" != "no" ] ; then
     bee_run check
 fi
 
+bee_fakeroot_start
+
 bee_run install
 
 print_info "changing to image directory: ${D}"
@@ -1102,6 +1188,8 @@ bee_crosscheck
 
 bee_pkg_pack
 
+bee_fakeroot_stop
+
 function bee_check_conflicts() {
     "${BEE_LIBEXECDIR}/bee/bee-cache-inventory" CONTENT \
         --prepend "${PKGALLPKG} " \