[PATCH 04/13] Makefile: use tempfile/mv strategy for GIT-*

[Jeff King <peff@peff.net>]

We create GIT-CFLAGS and related files by echoing into a
shell redirection. It's possible for an error to cause the
file to end up empty or truncated. In theory, this could
cause us to later make an incorrect comparison of the file
contents to a Makefile variable, and avoid rebuilding some
dependencies.

In practice, this is very unlikely to happen, as the
followup run would have to have changed the variable to
match the truncation exactly. However, it is good hygiene to
use our usual tempfile + mv trick to make sure that the file
is created atomically.

Signed-off-by: Jeff King <peff@peff.net>
---
 Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 50bf252..b06d5ec 100644
--- a/Makefile
+++ b/Makefile
@@ -1571,7 +1571,8 @@ GIT-$1: FORCE
 	@VALUE='$$(subst ','\'',$3)'; \
 	if test x"$$$$VALUE" != x"`cat $$@ 2>/dev/null`"; then \
 		echo >&2 "    * new $2"; \
-		echo "$$$$VALUE" >$$@; \
+		echo "$$$$VALUE" >$$@+ && \
+		mv $$@+ $$@; \
 	fi
 endef
 
-- 
1.8.5.2.500.g8060133