packaging: blindly factor out trap's cleanup function in builddeb

This commit blindly extracts builddeb's trap routine in a dedicated function.
While doing so, I think two bugs are exposed, which will be addressed in the
next commits:

- single quoting around '$CLEANUP' will always evaluate to the literal
  '$CLEANUP' regardless of the variable's value. The "if" will always be true.
- the removal operation will not expand $PWD (and a variable expansion would
  need double quotes, anyways.

contrib/packaging/builddeb

@@ -1,106 +1,113 b''
 #!/bin/sh -e
 #
 # Build a Mercurial debian package from the current repo
 #
 # Tested on Jessie (stable as of original script authoring.)
 
 . $(dirname $0)/packagelib.sh
 
 ROOTDIR=$(cd $(dirname $0)/../.. > /dev/null; pwd)
 
 BUILD=1
 CLEANUP=1
 DISTID=`(lsb_release -is 2> /dev/null | tr '[:upper:]' '[:lower:]') || echo debian`
 CODENAME=`lsb_release -cs 2> /dev/null || echo unknown`
 DEBFLAGS=-b
+
+cleanup() {
+    if [ '$CLEANUP' ]; then
+        rm -r '$PWD/debian';
+    fi
+}
+
 while [ "$1" ]; do
     case "$1" in
     --distid )
         shift
         DISTID="$1"
         shift
         ;;
     --codename )
         shift
         CODENAME="$1"
         shift
         ;;
     --cleanup )
         shift
         BUILD=
         ;;
     --build )
         shift
         CLEANUP=
         ;;
     --source-only )
         shift
         DEBFLAGS=-S
         ;;
     * )
         echo "Invalid parameter $1!" 1>&2
         exit 1
         ;;
     esac
 done
 
-trap "if [ '$CLEANUP' ] ; then rm -r '$PWD/debian' ; fi" EXIT
+trap 'cleanup' EXIT
 
 set -u
 
 if [ ! -d .hg ]; then
     printf "You are inside %s, which is not the root of a Mercurial repository\n" $(pwd) 1>&2
     exit 1
 fi
 
 gethgversion
 debver="$version"
 if [ -n "$type" ] ; then
     debver="$debver~$type"
 fi
 if [ -n "$distance" ] ; then
     debver="$debver+$distance-$CODENAME-$node"
 elif [ "$DEBFLAGS" = "-S" ] ; then
     # for building a ppa (--source-only) for a release (distance == 0), we need
     # to version the distroseries so that we can upload to launchpad
     debver="$debver~${CODENAME}1"
 fi
 
 control=debian/control
 changelog=debian/changelog
 
 if [ "$BUILD" ]; then
     if [ -d debian ] ; then
         printf "Error! debian control directory already exists at %s/debian\n" $(pwd)
         exit 1
     fi
 
     cp -r "$ROOTDIR"/contrib/packaging/debian debian
 
     sed -i.tmp "s/__VERSION__/$debver/" $changelog
     sed -i.tmp "s/__DATE__/$(date --rfc-2822)/" $changelog
     sed -i.tmp "s/__CODENAME__/$CODENAME/" $changelog
     rm $changelog.tmp
 
     # remove the node from the version string
     SRCFILE="mercurial_$(echo $debver | sed "s,-$node,,").orig.tar.gz"
     "$ROOTDIR/hg" archive $SRCFILE
     mv $SRCFILE ..
     debuild -us -uc -i -I $DEBFLAGS
     if [ $? != 0 ]; then
         echo 'debuild failed!'
         exit 1
     fi
 
 fi
 if [ "$CLEANUP" ] ; then
     echo
     OUTPUTDIR=${OUTPUTDIR:=packages/$DISTID-$CODENAME}
     mkdir -p "$OUTPUTDIR"
     find ../mercurial*.deb ../mercurial_*.build ../mercurial_*.changes \
           ../mercurial*.dsc ../mercurial*.gz \
           -type f -newer $control -print0 2>/dev/null | \
       xargs -Inarf -0 mv narf "$OUTPUTDIR"
     echo "Built packages for $debver:"
     find "$PWD"/"$OUTPUTDIR" -type f -newer $control -name '*.deb'
 fi