tags and cscope support really belongs in a shell script

as they do not benefit from the make functionality.

Moving the support to a shell script has several benefits:
- The readability of the code has increased a lot
- More people is able to extend the tags support
- We see less changes to the top-level Makefile

The shell script version includes improvements from:
Alexey Dobriyan <adobriyan@gmail.com> (jump to kconfig symbols)
Alexey Dobriyan <adobriyan@gmail.com> (drop ./ in paths)
Ian Campbell <ijc@hellion.org.uk> (simplified find algorithms)

This version has a few caveats:
=> It does not support ALLSOURCE_ARCHS
   - it is easy to add if it is really used
=> It assumes all archs have moved to arch/$ARCH/include
   - until that happens we have a few additional hits in the archs

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Tested-by: Ian Campbell <ijc@hellion.org.uk>

scripts/tags.sh

@@ -0,0 +1,160 @@
+#!/bin/sh
+# Generate tags or cscope files
+# Usage tags.sh <mode>
+#
+# mode may be any of: tags, TAGS, cscope
+#
+# Uses the following environment variables:
+# ARCH, SUBARCH, srctree, src, obj
+
+if [ $KBUILD_VERBOSE == 1 ]; then
+	set -x
+fi
+
+# This is a duplicate of RCS_FIND_IGNORE without escaped '()'
+ignore="( -name SCCS -o -name BitKeeper -o -name .svn -o \
+          -name CVS  -o -name .pc       -o -name .hg  -o \
+          -name .git )                                   \
+          -prune -o"
+
+# Do not use full path is we do not use O=.. builds
+if [ ${src} == ${obj} ]; then
+	tree=
+else
+	tree=${srctree}
+fi
+
+# find sources in arch/$ARCH
+find_arch_sources()
+{
+	find ${tree}arch/$1 $ignore -name $2 -print;
+}
+
+# find sources in arch/$1/include
+find_arch_include_sources()
+{
+	find ${tree}arch/$1/include $ignore -name $2 -print;
+}
+
+# find sources in include/
+find_include_sources()
+{
+	find ${tree}include $ignore -name config -prune -o -name $1 -print;
+}
+
+# find sources in rest of tree
+# we could benefit from a list of dirs to search in here
+find_other_sources()
+{
+	find ${tree}* $ignore \
+	     \( -name include -o -name arch -o -name '.tmp_*' \) -prune -o \
+	       -name $1 -print;
+}
+
+find_sources()
+{
+	find_arch_sources $1 $2
+	find_include_sources $2
+	find_other_sources $2
+}
+
+all_sources()
+{
+	find_sources $SRCARCH *.[chS]
+	if [ ! -z "$archinclude" ]; then
+		find_arch_include_sources $archinclude *.[chS]
+	fi
+}
+
+all_kconfigs()
+{
+	find_sources $SRCARCH "Kconfig*"
+}
+
+all_defconfigs()
+{
+	find_sources $SRCARCH "defconfig"
+}
+
+docscope()
+{
+	(echo \-k; echo \-q; all_sources) > cscope.files
+	cscope -b -f cscope.out
+}
+
+exuberant()
+{
+	all_sources > all
+	all_sources | xargs $1 -a                               \
+	-I __initdata,__exitdata,__acquires,__releases          \
+	-I __read_mostly,____cacheline_aligned                  \
+	-I ____cacheline_aligned_in_smp                         \
+	-I ____cacheline_internodealigned_in_smp                \
+	-I EXPORT_SYMBOL,EXPORT_SYMBOL_GPL                      \
+	--extra=+f --c-kinds=+px                                \
+	--regex-asm='/^ENTRY\(([^)]*)\).*/\1/'
+
+	all_kconfigs | xargs $1 -a                              \
+	--langdef=kconfig --language-force=kconfig              \
+	--regex-kconfig='/^[[:blank:]]*(menu|)config[[:blank:]]+([[:alnum:]_]+)/\2/'
+
+	all_kconfigs | xargs $1 -a                              \
+	--langdef=kconfig --language-force=kconfig              \
+	--regex-kconfig='/^[[:blank:]]*(menu|)config[[:blank:]]+([[:alnum:]_]+)/CONFIG_\2/'
+
+	all_defconfigs | xargs -r $1 -a                         \
+	--langdef=dotconfig --language-force=dotconfig          \
+	--regex-dotconfig='/^#?[[:blank:]]*(CONFIG_[[:alnum:]_]+)/\1/'
+
+}
+
+emacs()
+{
+	all_sources | xargs $1 -a
+
+	all_kconfigs | xargs $1 -a                              \
+	--regex='/^[ \t]*\(\(menu\)*config\)[ \t]+\([a-zA-Z0-9_]+\)/\3/'
+
+	all_kconfigs | xargs $1 -a                              \
+	--regex='/^[ \t]*\(\(menu\)*config\)[ \t]+\([a-zA-Z0-9_]+\)/CONFIG_\3/'
+
+	all_defconfigs | xargs -r $1 -a                         \
+	--regex='/^#?[ \t]?\(CONFIG_[a-zA-Z0-9_]+\)/\1/'
+}
+
+xtags()
+{
+	if $1 --version 2>&1 | grep -iq exuberant; then
+		exuberant $1
+	elif $1 --version 2>&1 | grep -iq emacs; then
+		emacs $1
+	else
+		all_sources | xargs $1 -a
+        fi
+}
+
+
+# Support um (which uses SUBARCH)
+if [ ${ARCH} == um ]; then
+	if [ $SUBARCH == i386 ]; then
+		archinclude=x86
+	elif [ $SUBARCH == x86_64 ]; then
+		archinclude=x86
+	else
+		archinclude=${SUBARCH}
+	fi
+fi
+
+case "$1" in
+	"cscope")
+		docscope
+		;;
+
+	"tags")
+		xtags ctags
+		;;
+
+	"TAGS")
+		xtags etags
+		;;
+esac