[RFC PATCH] Makefile: add GNU global tags support

["Alex Bennée" <alex.bennee@linaro.org>]

GNU Global is another tags engine which is more like cscope in being
able to support finding both references and definitions. You will be
un-surprised to know it also integrates well with Emacs.

The main benefit of integrating it into find-src-path is it takes less
time to rebuild the database from scratch when you have a lot of build
directories under your source tree.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 Makefile   | 9 ++++++++-
 .gitignore | 3 +++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index fb9923ff22..66eec99685 100644
--- a/Makefile
+++ b/Makefile
@@ -253,6 +253,13 @@ ctags:
 	rm -f "$(SRC_PATH)/"tags
 	$(find-src-path) -exec ctags -f "$(SRC_PATH)/"tags --append {} +
 
+.PHONY: gtags
+gtags:
+	rm -f "$(SRC_PATH)/"GTAGS
+	rm -f "$(SRC_PATH)/"GRTAGS
+	rm -f "$(SRC_PATH)/"GPATH
+	$(find-src-path) | gtags -f -
+
 .PHONY: TAGS
 TAGS:
 	rm -f "$(SRC_PATH)/"TAGS
@@ -279,7 +286,7 @@ help:
 	$(call print-help,all,Build all)
 	$(call print-help,dir/file.o,Build specified target only)
 	$(call print-help,install,Install QEMU, documentation and tools)
-	$(call print-help,ctags/TAGS,Generate tags file for editors)
+	$(call print-help,ctags/gtags/TAGS,Generate tags file for editors)
 	$(call print-help,cscope,Generate cscope index)
 	$(call print-help,sparse,Run sparse on the QEMU source)
 	@echo  ''
diff --git a/.gitignore b/.gitignore
index b32bca1315..75a4be0724 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,9 @@
 cscope.*
 tags
 TAGS
+GPATH
+GRTAGS
+GTAGS
 *~
 *.ast_raw
 *.depend_raw
-- 
2.20.1