[PATCH 3/3] kbuild: Add a build check for missing gitignore entries

[Rob Herring]

Any non-phony targets need to be in gitignore. The normal way to check
this is doing an in-tree build and running git-status which is easy to
miss. Git provides an easy way to check whether a file is ignored with
git-check-ignore. Let's add a build time check using it. If the build is
not in a git tree, the check will silently fail.

This also has the side effect of a sanity check for 'always-y',
'extra-y' and 'targets' entries which are not correctly marked as PHONY
or have the wrong path.

Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
Cc: linux-kbuild@xxxxxxxxxxxxxxx
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
---
 scripts/Makefile.lib | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index b00855b247e0..84ac8b74bbe9 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -103,6 +103,10 @@ real-obj-m	:= $(addprefix $(obj)/,$(real-obj-m))
 multi-used-m	:= $(addprefix $(obj)/,$(multi-used-m))
 subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
 
+$(foreach f, $(filter-out $(patsubst %,$(obj)/%,$(PHONY)),$(extra-y) $(always-y) $(targets)), \
+	$(if $(shell git -C $(srctree) check-ignore -q $(f) 2> /dev/null || echo $(f)), \
+		$(warning $(f) is missing gitignore entry)))
+
 # Finds the multi-part object the current object will be linked into.
 # If the object belongs to two or more multi-part objects, list them all.
 modname-multi = $(sort $(foreach m,$(multi-used),\
-- 
2.27.0