more build avoidance for rebar build

Modify scripts/rebar-pre-scripts and scripts/local-install to avoid
rebuilding generated files that haven't changed since the last
build. Modify scripts/Makefile to account for local-install changes.

Also apply minor fix to rebar.config indentation.

rebar.config

@@ -7,7 +7,7 @@
 
 {port_envs, [{"CFLAGS", "$CFLAGS -g -O3 -Wall -I/usr/include/security"},
              {"(linux|freebsd|dragonfly|solaris|darwin)",
-             "DRV_CFLAGS", "$DRV_CFLAGS -DHAVE_SENDFILE"}]}.
+              "DRV_CFLAGS", "$DRV_CFLAGS -DHAVE_SENDFILE"}]}.
 
 {so_specs, [{"priv/lib/epam.so", ["c_src/epam.o"]},
             {"priv/lib/setuid_drv.so", ["c_src/setuid_drv.o"]},

scripts/Makefile

@@ -10,7 +10,7 @@ all debug:	../bin/yaws yaws.conf
 
 
 local_install:	../bin/yaws
-	VARDIR='$(VARDIR)' ./local-install
+	VARDIR='$(VARDIR)' ./local-install true
 
 yaws.conf:
 	YAWSDIR='$(PREFIX)/lib/yaws' LOGDIR='$(PREFIX)/var/log/yaws' \

scripts/local-install

@@ -13,23 +13,35 @@ if [ -z "$HOME" ]; then
     fi
 fi
 
+script=`basename $0`
+tmpgen=`mktemp /tmp/${script}.XXXXXX`
+
 logdir="${HOME}/yaws_logs"
 [ -d $logdir ] || mkdir $logdir
+overwrite=true
 if [ -f "${HOME}/yaws.conf" ]; then
-    echo "--- Will not overwrite ${HOME}/yaws.conf"
+    overwrite=false
     target="${HOME}/yaws.conf.template"
 else
     target="${HOME}/yaws.conf"
 fi
-echo "--- Installing local config file at $target"
 
 topdir=`cd .. && pwd`
 YAWSDIR="$topdir" LOGDIR="$logdir" VARDIR="$VARDIR" PORT=8000 \
     DOCROOT="${topdir}/www" CERTDIR="${topdir}/ssl" SSLPORT=4443 \
-    ./gen-yaws-conf > $target
-[ -d "${HOME}/bin" ] || mkdir "${HOME}/bin"
-rm -f "${HOME}/bin/yaws"
-cp -f ../bin/yaws "${HOME}/bin/yaws"
-echo "--- Installed $HOME/bin/yaws"
+    ./gen-yaws-conf > $tmpgen
+if [ -f "$target" ] && cmp -s "$target" "$tmpgen"; then
+    rm -f "$tmpgen"
+else
+    mv -f "$tmpgen" "$target"
+    [ $overwrite = false ] && echo "--- Will not overwrite ${HOME}/yaws.conf"
+    echo "--- Installing local config file at $target"
+fi
+if [ "$1" = true ] || [ ! -f "${HOME}/bin/yaws" ]; then
+    [ -d "${HOME}/bin" ] || mkdir "${HOME}/bin"
+    rm -f "${HOME}/bin/yaws"
+    cp -f ../bin/yaws "${HOME}/bin/yaws"
+    echo "--- Installed $HOME/bin/yaws"
+fi
 
 exit 0

scripts/rebar-pre-script

@@ -14,6 +14,8 @@ WERL_BIN=$YAWS_ERLBINDIR/werl
 # For rebar, support only local install for the yaws script.
 YAWS_LOCALINSTALL=true
 
+script=`basename $0`
+
 # Use a function for error exit instead of set -e so we can conditionally
 # remove files before exiting. If this were bash we could trap ERR but
 # Bourne shell doesn't support that portably.
@@ -22,6 +24,16 @@ fail() {
     exit 1
 }
 
+keep_or_replace() {
+    if [ -f "$1" ] && cmp -s "$1" "$2"; then
+        rm -f "$2"
+        return 0
+    else
+        mv "$2" "$1" || fail "$2"
+        return 1
+    fi
+}
+
 cd src || fail
 
 if [ "$1" = clean ]; then
@@ -45,19 +57,27 @@ if [ ! -f yaws_configure.hrl ]; then
     echo '%% rebar sets HAVE_SENDFILE in erlc command line' > yaws_configure.hrl
     [ $? -eq 0 ] || fail
 fi
+tmpgen=`mktemp /tmp/${script}.XXXXXX` || fail
 YAWS_VSN=$YAWS_VSN VARDIR="$YAWS_VARDIR" ETCDIR="$YAWS_ETCDIR" \
-    ../scripts/gen-yaws-generated $YAWS_LOCALINSTALL >yaws_generated.erl || fail
+    ../scripts/gen-yaws-generated $YAWS_LOCALINSTALL >$tmpgen || fail
+keep_or_replace yaws_generated.erl $tmpgen
 [ -d "$YAWS_VARDIR" ] || mkdir "$YAWS_VARDIR" || fail
 [ -d "$YAWS_ETCDIR" ] || mkdir "$YAWS_ETCDIR" || fail
 
 cd ../scripts
 
 case $YAWS_LOCALINSTALL in
     true)
+        tmpgen=`mktemp /tmp/${script}.XXXXXX` || fail
         VARDIR="${YAWS_VARDIR}" ERLBINDIR="${YAWS_ERLBINDIR}" \
-            ERL="${ERL_BIN}" WERL="${WERL_BIN}" ./gen-yaws > ../bin/yaws || fail
-        test -x ../bin/yaws || chmod +x ../bin/yaws || fail
-        VARDIR="${YAWS_VARDIR}" ./local-install || fail
+            ERL="${ERL_BIN}" WERL="${WERL_BIN}" ./gen-yaws > $tmpgen || fail
+        keep_or_replace ../bin/yaws $tmpgen
+        if [ $? -eq 0 ]; then
+            VARDIR="${YAWS_VARDIR}" ./local-install false || fail
+        else
+            chmod +x ../bin/yaws || fail
+            VARDIR="${YAWS_VARDIR}" ./local-install true || fail
+        fi
        ;;
     *)
        echo "ERROR: Configurations other than 'localinstall' not yet \