sparse: Fix errors and silence warnings

* load_file() returns a void pointer but is using 0 for the return
   value

 * builtin/receive-pack.c forgot to include builtin.h

 * packet_trace_prefix can be marked static

 * ll_merge takes a pointer for its last argument, not an int

 * crc32 expects a pointer as the second argument but Z_NULL is defined
   to be 0 (see 38f4d13 sparse fix: Using plain integer as NULL pointer,
   2006-11-18 for more info)

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/grep.c

@@ -414,10 +414,10 @@ static void *load_file(const char *filename, size_t *sz)
 	err_ret:
 		if (errno != ENOENT)
 			error(_("'%s': %s"), filename, strerror(errno));
-		return 0;
+		return NULL;
 	}
 	if (!S_ISREG(st.st_mode))
-		return 0;
+		return NULL;
 	*sz = xsize_t(st.st_size);
 	i = open(filename, O_RDONLY);
 	if (i < 0)
@@ -427,7 +427,7 @@ static void *load_file(const char *filename, size_t *sz)
 		error(_("'%s': short read %s"), filename, strerror(errno));
 		close(i);
 		free(data);
-		return 0;
+		return NULL;
 	}
 	close(i);
 	data[*sz] = 0;

builtin/index-pack.c

@@ -294,7 +294,7 @@ static void *unpack_raw_entry(struct object_entry *obj, union delta_base *delta_
 	void *data;
 
 	obj->idx.offset = consumed_bytes;
-	input_crc32 = crc32(0, Z_NULL, 0);
+	input_crc32 = crc32(0, NULL, 0);
 
 	p = fill(1);
 	c = *p;

builtin/receive-pack.c

@@ -1,4 +1,4 @@
-#include "cache.h"
+#include "builtin.h"
 #include "pack.h"
 #include "refs.h"
 #include "pkt-line.h"

csum-file.c

@@ -116,7 +116,7 @@ struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp
 
 void crc32_begin(struct sha1file *f)
 {
-	f->crc32 = crc32(0, Z_NULL, 0);
+	f->crc32 = crc32(0, NULL, 0);
 	f->do_crc = 1;
 }
 

pack-check.c

@@ -23,7 +23,7 @@ int check_pack_crc(struct packed_git *p, struct pack_window **w_curs,
 		   off_t offset, off_t len, unsigned int nr)
 {
 	const uint32_t *index_crc;
-	uint32_t data_crc = crc32(0, Z_NULL, 0);
+	uint32_t data_crc = crc32(0, NULL, 0);
 
 	do {
 		unsigned int avail;

pkt-line.c

@@ -1,7 +1,7 @@
 #include "cache.h"
 #include "pkt-line.h"
 
-const char *packet_trace_prefix = "git";
+static const char *packet_trace_prefix = "git";
 static const char trace_key[] = "GIT_TRACE_PACKET";
 
 void packet_trace_identity(const char *prog)

rerere.c

@@ -438,7 +438,7 @@ static int merge(const char *name, const char *path)
 		ret = 1;
 		goto out;
 	}
-	ret = ll_merge(&result, path, &base, NULL, &cur, "", &other, "", 0);
+	ret = ll_merge(&result, path, &base, NULL, &cur, "", &other, "", NULL);
 	if (!ret) {
 		FILE *f;