Makefile: add ability to append to CFLAGS and LDFLAGS

There are some usecases where we may want to append CFLAGS to the
default CFLAGS set by Git. This could for example be to enable or
disable specific compiler warnings or to change the optimization level
that code is compiled with. This cannot be done without overriding the
complete CFLAGS value though and thus requires the user to redeclare the
complete defaults used by Git.

Introduce a new variable `CFLAGS_APPEND` that gets appended to the
default value of `CFLAGS`. As compiler options are last-one-wins, this
fulfills both of the usecases mentioned above. It's also common practice
across many other projects to have such a variable.

While at it, also introduce a matching `LDFLAGS_APPEND` variable. While
there isn't really any need for this variable as there are no default
`LDFLAGS`, users may expect this variable to exist, as well.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Makefile b/Makefile
index 1e31acc72eca23274f6ca0b00347f5de12f3a4e6..f148b4309bb44180d721a2bc39451b33ba72dae8 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -1458,8 +1458,8 @@ ALL_COMMANDS_TO_INSTALL += git-upload-archive$(X)
 ALL_COMMANDS_TO_INSTALL += git-upload-pack$(X)
 endif
 
-ALL_CFLAGS = $(DEVELOPER_CFLAGS) $(CPPFLAGS) $(CFLAGS)
-ALL_LDFLAGS = $(LDFLAGS)
+ALL_CFLAGS = $(DEVELOPER_CFLAGS) $(CPPFLAGS) $(CFLAGS) $(CFLAGS_APPEND)
+ALL_LDFLAGS = $(LDFLAGS) $(LDFLAGS_APPEND)
 
 ifdef SANITIZE
 SANITIZERS := $(foreach flag,$(subst $(comma),$(space),$(SANITIZE)),$(flag))