make it possible to keep usage texts in .c files

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/scripts/Makefile.IMA b/scripts/Makefile.IMA
index bddd702..11ae39e 100644
--- a/scripts/Makefile.IMA
+++ b/scripts/Makefile.IMA
@@ -200,7 +200,7 @@
 applets/applet_tables: include/autoconf.h
 	$(HOSTCC) -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -I$(srctree)/include -o applets/applet_tables applets/applet_tables.c
 
-include/usage_compressed.h: $(srctree)/include/usage.h applets/usage
+include/usage_compressed.h: include/usage.h applets/usage
 	$(srctree)/applets/usage_compressed include/usage_compressed.h applets
 
 include/applet_tables.h: include/applets.h
diff --git a/scripts/gen_build_files.sh b/scripts/gen_build_files.sh
index 44e8c17..647c7da 100755
--- a/scripts/gen_build_files.sh
+++ b/scripts/gen_build_files.sh
@@ -10,7 +10,7 @@
 # (Re)generate include/applets.h
 src="$srctree/include/applets.src.h"
 dst="include/applets.h"
-s=`sed -n 's@^//applet:@@p' -- */*.c */*/*.c`
+s=`sed -n 's@^//applet:@@p' -- "$srctree"/*/*.c "$srctree"/*/*/*.c`
 echo "/* DO NOT EDIT. This file is generated from applets.src.h */" >"$dst.$$.tmp"
 # Why "IFS='' read -r REPLY"??
 # This atrocity is needed to read lines without mangling.
@@ -27,6 +27,30 @@
 	mv -- "$dst.$$.tmp" "$dst"
 fi
 
+# (Re)generate include/usage.h
+src="$srctree/include/usage.src.h"
+dst="include/usage.h"
+# We add line continuation backslash after each line,
+# and insert empty line before each line which doesn't start
+# with space or tab
+# (note: we need to use \\\\ because of ``)
+s=`sed -n -e 's@^//usage:\([ \t].*\)$@\1 \\\\@p' -e 's@^//usage:\([^ \t].*\)$@\n\1 \\\\@p' -- "$srctree"/*/*.c "$srctree"/*/*/*.c`
+echo "/* DO NOT EDIT. This file is generated from usage.src.h */" >"$dst.$$.tmp"
+# Why "IFS='' read -r REPLY"??
+# This atrocity is needed to read lines without mangling.
+# IFS='' prevents whitespace trimming,
+# -r suppresses backslash handling.
+while IFS='' read -r REPLY; do
+	test x"$REPLY" = x"INSERT" && REPLY="$s"
+	printf "%s\n" "$REPLY"
+done <"$src" >>"$dst.$$.tmp"
+if test -f "$dst" && cmp -s "$dst.$$.tmp" "$dst"; then
+	rm -- "$dst.$$.tmp"
+else
+	echo "  GEN     $dst"
+	mv -- "$dst.$$.tmp" "$dst"
+fi
+
 # (Re)generate */Kbuild and */Config.in
 find -type d | while read -r d; do
 	d="${d#./}"