utils/config: new script to manipulate .config files on the command line

Default prefix is set to `BR2_` but may be overidden by setting
BR2_PREFIX.

Example usage:

Enable `BR2_PACKAGE_GNUPG`:
./utils/config --package --enable GNUPG

Check state of config option `BR2_PACKAGE_GNUPG`:
./utils/config --package --state GNUPG
y

Enable `BR2_PACKAGE_GNUPG`:
./utils/config --package --disable GNUPG

Set `BR2_TARGET_GENERIC_ISSUE` to "Welcome":
./utils/config --set-str  TARGET_GENERIC_ISSUE "Welcome"

Copied from the Linux kernel (4.13-rc6) source code and adapted to
Buildroot.
Thanks to Andi Kleen who is the original author of this script.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
[Arnout: merge the two tr invications]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

diff --git a/utils/config b/utils/config
new file mode 100755 (executable)
index 0000000..c5e2d72
--- /dev/null
+++ b/utils/config
@@ -0,0 +1,206 @@
+#!/bin/bash
+# Manipulate options in a .config file from the command line
+
+myname=${0##*/}
+
+# If no prefix forced, use the default BR2_
+BR2_PREFIX="${BR2_PREFIX-BR2_}"
+
+usage() {
+       cat >&2 <<EOL
+Manipulate options in a .config file from the command line.
+Usage:
+$myname options command ...
+commands:
+       --enable|-e option   Enable option
+       --disable|-d option  Disable option
+       --set-str option string
+                            Set option to "string"
+       --set-val option value
+                            Set option to value
+       --undefine|-u option Undefine option
+       --state|-s option    Print state of option (n,y,m,undef)
+
+       --enable-after|-E beforeopt option
+                             Enable option directly after other option
+       --disable-after|-D beforeopt option
+                             Disable option directly after other option
+
+       commands can be repeated multiple times
+
+options:
+       --file config-file   .config file to change (default .config)
+       --keep-case|-k       Keep next symbols' case (dont' upper-case it)
+       --package|-p         Operate on package (set prefix to BR2_PACKAGE_)
+
+$myname doesn't check the validity of the .config file. This is done at next
+make time.
+
+By default, $myname will upper-case the given symbol. Use --keep-case to keep
+the case of all following symbols unchanged.
+
+$myname uses 'BR2_' as the default symbol prefix. Set the environment
+variable BR2_PREFIX to the prefix to use. Eg.: BR2_PREFIX="FOO_" $myname ...
+EOL
+       exit 1
+}
+
+checkarg() {
+       ARG="$1"
+       if [ "$ARG" = "" ] ; then
+               usage
+       fi
+       if [ "$MUNGE_CASE" = "yes" ] ; then
+               ARG="`echo $ARG | tr a-z- A-Z_`"
+       fi
+       case "$ARG" in
+       ${BR2_PREFIX}*)
+               ARG="${ARG/${BR2_PREFIX}/}"
+               ;;
+       esac
+}
+
+txt_append() {
+       local anchor="$1"
+       local insert="$2"
+       local infile="$3"
+       local tmpfile="$infile.swp"
+
+       # sed append cmd: 'a\' + newline + text + newline
+       cmd="$(printf "a\\%b$insert" "\n")"
+
+       sed -i -e "/$anchor/$cmd" "$infile"
+}
+
+txt_subst() {
+       local before="$1"
+       local after="$2"
+       local infile="$3"
+       local tmpfile="$infile.swp"
+
+       sed -i -e "s:$before:$after:" "$infile"
+}
+
+txt_delete() {
+       local text="$1"
+       local infile="$2"
+       local tmpfile="$infile.swp"
+
+       sed -i -e "/$text/d" "$infile"
+}
+
+set_var() {
+       local name=$1 new=$2 before=$3
+
+       name_re="^($name=|# $name is not set)"
+       before_re="^($before=|# $before is not set)"
+       if test -n "$before" && grep -Eq "$before_re" "$FN"; then
+               txt_append "^$before=" "$new" "$FN"
+               txt_append "^# $before is not set" "$new" "$FN"
+       elif grep -Eq "$name_re" "$FN"; then
+               txt_subst "^$name=.*" "$new" "$FN"
+               txt_subst "^# $name is not set" "$new" "$FN"
+       else
+               echo "$new" >>"$FN"
+       fi
+}
+
+undef_var() {
+       local name=$1
+
+       txt_delete "^$name=" "$FN"
+       txt_delete "^# $name is not set" "$FN"
+}
+
+if [ "$1" = "--file" ]; then
+       FN="$2"
+       if [ "$FN" = "" ] ; then
+               usage
+       fi
+       shift 2
+else
+       FN=.config
+fi
+
+if [ "$1" = "" ] ; then
+       usage
+fi
+
+MUNGE_CASE=yes
+while [ "$1" != "" ] ; do
+       CMD="$1"
+       shift
+       case "$CMD" in
+       --keep-case|-k)
+               MUNGE_CASE=no
+               continue
+               ;;
+       --package|-p)
+               BR2_PREFIX="BR2_PACKAGE_"
+               continue
+               ;;
+       --*-after|-E|-D|-M)
+               checkarg "$1"
+               A=$ARG
+               checkarg "$2"
+               B=$ARG
+               shift 2
+               ;;
+       -*)
+               checkarg "$1"
+               shift
+               ;;
+       esac
+       case "$CMD" in
+       --enable|-e)
+               set_var "${BR2_PREFIX}$ARG" "${BR2_PREFIX}$ARG=y"
+               ;;
+
+       --disable|-d)
+               set_var "${BR2_PREFIX}$ARG" "# ${BR2_PREFIX}$ARG is not set"
+               ;;
+
+       --set-str)
+               # sed swallows one level of escaping, so we need double-escaping
+               set_var "${BR2_PREFIX}$ARG" "${BR2_PREFIX}$ARG=\"${1//\"/\\\\\"}\""
+               shift
+               ;;
+
+       --set-val)
+               set_var "${BR2_PREFIX}$ARG" "${BR2_PREFIX}$ARG=$1"
+               shift
+               ;;
+       --undefine|-u)
+               undef_var "${BR2_PREFIX}$ARG"
+               ;;
+
+       --state|-s)
+               if grep -q "# ${BR2_PREFIX}$ARG is not set" $FN ; then
+                       echo n
+               else
+                       V="$(grep "^${BR2_PREFIX}$ARG=" $FN)"
+                       if [ $? != 0 ] ; then
+                               echo undef
+                       else
+                               V="${V/#${BR2_PREFIX}$ARG=/}"
+                               V="${V/#\"/}"
+                               V="${V/%\"/}"
+                               V="${V//\\\"/\"}"
+                               echo "${V}"
+                       fi
+               fi
+               ;;
+
+       --enable-after|-E)
+               set_var "${BR2_PREFIX}$B" "${BR2_PREFIX}$B=y" "${BR2_PREFIX}$A"
+               ;;
+
+       --disable-after|-D)
+               set_var "${BR2_PREFIX}$B" "# ${BR2_PREFIX}$B is not set" "${BR2_PREFIX}$A"
+               ;;
+
+       *)
+               usage
+               ;;
+       esac
+done