conf/layer.conf: Use .= for BBPATH and += for BBFILES

Provide additional commentary that should help a bit more
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Acked-by: Paul Menzel <paulepanter@users.sourceforge.net>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>

meta-efl/conf/layer.conf

-# We have a conf and classes directory, prepend to BBPATH to prefer our versions
-BBPATH := "${LAYERDIR}:${BBPATH}"
+# We have a conf and classes directory, append to BBPATH 
+BBPATH .= ":${LAYERDIR}"
 
 # We have a recipes directory, add to BBFILES
-BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
+BBFILES += "${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
 
 BBFILE_COLLECTIONS += "efl-layer"
 BBFILE_PATTERN_efl-layer := "^${LAYERDIR}/"

meta-gnome/conf/layer.conf

-# We have a conf and classes directory, prepend to BBPATH to prefer our versions
-BBPATH := "${LAYERDIR}:${BBPATH}"
+# We have a conf and classes directory, append to BBPATH
+BBPATH .= ":${LAYERDIR}"
 
 # We have a recipes directory, add to BBFILES
-BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
+BBFILES += "${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
 
 BBFILE_COLLECTIONS += "gnome-layer"
 BBFILE_PATTERN_gnome-layer := "^${LAYERDIR}/"

meta-gpe/conf/layer.conf

-# We have a conf and classes directory, prepend to BBPATH to prefer our versions
-BBPATH := "${LAYERDIR}:${BBPATH}"
+# We have a conf and classes directory, append to BBPATH
+BBPATH .= ":${LAYERDIR}"
 
 # We have a recipes directory, add to BBFILES
-BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
+BBFILES += "${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
 
 BBFILE_COLLECTIONS += "gpe-layer"
 BBFILE_PATTERN_gpe-layer := "^${LAYERDIR}/"

meta-oe/conf/layer.conf

-# We have a conf and classes directory, prepend to BBPATH to prefer our versions
-BBPATH := "${LAYERDIR}:${BBPATH}"
+# It really depends on order of the layers appearing in BBLAYERS
+# variable in toplevel bblayers.conf file, where bitbake will search
+# for .inc files and others where bitbake uses BBPATH since it will
+# search the directories from first to last as specified in BBPATH
+# Therefore if you want a given layer to be considered high priority
+# for the .inc and .conf etc. then consider it adding at the beginning
+# of BBPATH. For bblayers bitbake will use BBFILES_PRIORITY to resolve
+# the recipe contention so the order of directories in BBFILES does 
+# not matter.
+
+# We have a conf and classes directory, append to BBPATH
+BBPATH .= ":${LAYERDIR}"
 
 # We have a recipes directory, add to BBFILES
-BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
+BBFILES += "${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
 
 BBFILE_COLLECTIONS += "openembedded-layer"
 BBFILE_PATTERN_openembedded-layer := "^${LAYERDIR}/"
+
+# Define the priority for recipes (.bb files) from this layer,
+# choosing carefully how this layer interacts with all of the
+# other layers.
+
 BBFILE_PRIORITY_openembedded-layer = "6"