git-compat-util: move include of "compat/zlib.h" into "git-zlib.h"

We include "compat/zlib.h" in "git-compat-util.h", which is
unnecessarily broad given that we only have a small handful of files
that use the zlib library. Move the header into "git-zlib.h" instead and
adapt users of zlib to include that header.

One exception is the reftable library, as we don't want to use the
Git-specific wrapper of zlib there, so we include "compat/zlib.h"
instead. Furthermore, we move the include into "reftable/system.h" so
that users of the library other than Git can wire up zlib themselves.

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

archive.c

@@ -7,6 +7,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "hex.h"
 #include "object-name.h"
 #include "path.h"

config.c

@@ -19,6 +19,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "ident.h"
 #include "repository.h"
 #include "lockfile.h"

csum-file.c

@@ -11,9 +11,10 @@
 #define USE_THE_REPOSITORY_VARIABLE
 
 #include "git-compat-util.h"
-#include "progress.h"
 #include "csum-file.h"
+#include "git-zlib.h"
 #include "hash.h"
+#include "progress.h"
 
 static void verify_buffer_or_die(struct hashfile *f,
 				 const void *buf,

environment.c

@@ -16,6 +16,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "repository.h"
 #include "config.h"
 #include "refs.h"

git-compat-util.h

@@ -1537,8 +1537,6 @@ int cmd_main(int, const char **);
 int common_exit(const char *file, int line, int code);
 #define exit(code) exit(common_exit(__FILE__, __LINE__, (code)))
 
-#include "compat/zlib-compat.h"
-
 /*
  * This include must come after system headers, since it introduces macros that
  * replace system names.

git-zlib.h

@@ -1,6 +1,8 @@
 #ifndef GIT_ZLIB_H
 #define GIT_ZLIB_H
 
+#include "compat/zlib-compat.h"
+
 typedef struct git_zstream {
 	z_stream z;
 	unsigned long avail_in;

reftable/block.c

@@ -13,7 +13,6 @@ https://developers.google.com/open-source/licenses/bsd
 #include "record.h"
 #include "reftable-error.h"
 #include "system.h"
-#include "compat/zlib-compat.h"
 
 int header_size(int version)
 {

reftable/system.h

@@ -14,6 +14,7 @@ https://developers.google.com/open-source/licenses/bsd
 #define DISABLE_SIGN_COMPARE_WARNINGS
 
 #include "git-compat-util.h"
+#include "compat/zlib-compat.h"
 
 /*
  * An implementation-specific temporary file. By making this specific to the