[Buildroot] [PATCH 03/16 v3] core/pkg-utils: add macro to hardlink-or-copy

[Yann E. MORIN]

This macro will try to copy a source file into a destination fdirectory,
by first atempting a hard-link, and falling back to a plain copy.

In some situations, it will be necessary that the destination file is
named differently than the source (e.g. due to a re-numbering), so if a
third argument is specified, it is treated as the basename of the
destination file.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: Luca Ceresoli <luca at lucaceresoli.net>

---
Changes v2 -> v3;
  - use "ln" instead of "cp -l"
  - accept third argument, as the basename of the destination file
  - drop reviewed-by and tested-by tags given in v2, due to the above
    two changes

Changes RFC -> v1:
  - move to pkg-utils  (Luca)
---
 package/pkg-utils.mk | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/package/pkg-utils.mk b/package/pkg-utils.mk
index 44bd2c9..6479cd8 100644
--- a/package/pkg-utils.mk
+++ b/package/pkg-utils.mk
@@ -113,6 +113,31 @@ $$(error Package error: use $(2) instead of $(1). Please fix your .mk file)
 endif
 endef
 
+################################################################################
+# hardlink-copy -- hardlink source and destination if possible, otherwise
+# do a simple copy
+#
+# argument 1 is the source *file*
+# argument 2 is the destination *directory*
+# argument 3 is the basename of the destination file (optional, defaults to
+#            the basename of the source file.
+#
+# examples:
+#   $(call hardlink-copy,/path/to/source/file,/path/to/destination/dir/)
+#   $(call hardlink-copy,/path/to/source/file,/path/to/destination/dir/,new-name)
+#
+# Note: we make that a single command, so se can:
+#  - use '$(Q)' in front of it and properly silence the whole macro,
+#  - use '|| exit 1' after it, so we can exit on error in compound commands.
+################################################################################
+define hardlink-copy
+	{ mkdir -p $(2) && \
+		{ ln $(1) $(2)$(if $(3),/$(strip $(3))) 2>/dev/null || \
+		  cp $(1) $(2)$(if $(3),/$(strip $(3))); \
+		} \
+	}
+endef
+
 #
 # legal-info helper functions
 #
-- 
1.9.1