makefile: Add a cscope target

The current makefile supports ctags but not cscope. Some people prefer
cscope (I do), so this patch adds a cscope target.

I've also added cscope* to the .gitignore file. For some reason tags
and TAGS weren't in there either so I've added them too.

Signed-off-by: Kristof Provost <Kristof@provost-engineering.be>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

.gitignore

@@ -171,3 +171,6 @@ config.status
 config.mak.autogen
 config.mak.append
 configure
+tags
+TAGS
+cscope*

Makefile

@@ -947,6 +947,10 @@ tags:
 	$(RM) tags
 	$(FIND) . -name '*.[hcS]' -print | xargs ctags -a
 
+cscope:
+	$(RM) cscope*
+	$(FIND) . -name '*.[hcS]' -print | xargs cscope -b
+
 ### Detect prefix changes
 TRACK_CFLAGS = $(subst ','\'',$(ALL_CFLAGS)):\
              $(bindir_SQ):$(gitexecdir_SQ):$(template_dir_SQ):$(prefix_SQ)
@@ -1093,7 +1097,7 @@ clean:
 		$(LIB_FILE) $(XDIFF_LIB)
 	$(RM) $(ALL_PROGRAMS) $(BUILT_INS) git$X
 	$(RM) $(TEST_PROGRAMS)
-	$(RM) *.spec *.pyc *.pyo */*.pyc */*.pyo common-cmds.h TAGS tags
+	$(RM) *.spec *.pyc *.pyo */*.pyc */*.pyo common-cmds.h TAGS tags cscope*
 	$(RM) -r autom4te.cache
 	$(RM) configure config.log config.mak.autogen config.mak.append config.status config.cache
 	$(RM) -r $(GIT_TARNAME) .doc-tmp-dir
@@ -1111,7 +1115,7 @@ endif
 	$(RM) GIT-VERSION-FILE GIT-CFLAGS GIT-GUI-VARS
 
 .PHONY: all install clean strip
-.PHONY: .FORCE-GIT-VERSION-FILE TAGS tags .FORCE-GIT-CFLAGS
+.PHONY: .FORCE-GIT-VERSION-FILE TAGS tags cscope .FORCE-GIT-CFLAGS
 
 ### Check documentation
 #