[Buildroot] [PATCH 1/6 RFC] core/pkg-generic: allow packages to exclude files when extracting

[Yann E. MORIN]

Currently, packages that need to exclude parts of the archives when
extracting (e.g. to gain space), like gcc or toolchain-external, have to
provide custom extract commands, just for the sake of adding a bunch of
--exclude directives when calling tar.

Add a new variable that packages may set, to provide a space-separated
list of patterns to exclude.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Cc: Vicente Olivert Riera <Vincent.Riera at imgtec.com>
---
 docs/manual/adding-packages-generic.txt | 4 ++++
 package/pkg-generic.mk                  | 5 ++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/docs/manual/adding-packages-generic.txt b/docs/manual/adding-packages-generic.txt
index 4c12b42..e7a473c 100644
--- a/docs/manual/adding-packages-generic.txt
+++ b/docs/manual/adding-packages-generic.txt
@@ -312,6 +312,10 @@ information is (assuming the package name is +libfoo+) :
   that have more than one leading component to strip, set this
   variable with the value to be passed to tar. Default: 1.
 
+* +LIBFOO_EXCLUDES+ is a space-separated list of patterns to exclude
+  when extracting the archive. Each item from that list is passed as
+  a tar's +--exclude+ option. By default, empty.
+
 * +LIBFOO_DEPENDENCIES+ lists the dependencies (in terms of package
   name) that are required for the current target package to
   compile. These dependencies are guaranteed to be compiled and
diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
index 6a7d97e..d1877a7 100644
--- a/package/pkg-generic.mk
+++ b/package/pkg-generic.mk
@@ -476,7 +476,10 @@ $(2)_TARGET_DIRCLEAN =		$$($(2)_DIR)/.stamp_dircleaned
 # default extract command
 $(2)_EXTRACT_CMDS ?= \
 	$$(if $$($(2)_SOURCE),$$(INFLATE$$(suffix $$($(2)_SOURCE))) $$(DL_DIR)/$$($(2)_SOURCE) | \
-	$$(TAR) --strip-components=$$($(2)_STRIP_COMPONENTS) -C $$($(2)_DIR) $$(TAR_OPTIONS) -)
+	$$(TAR) --strip-components=$$($(2)_STRIP_COMPONENTS) \
+		-C $$($(2)_DIR) \
+		$$(foreach x,$$($(2)_EXCLUDES),--exclude='$$(x)' ) \
+		$$(TAR_OPTIONS) -)
 
 # pre/post-steps hooks
 $(2)_PRE_DOWNLOAD_HOOKS         ?=
-- 
1.9.1