sha1_file: add a "read_sha1_file_repl" function

This new function will replace "read_sha1_file". This latter function
becoming just a stub to call the former will a NULL "replacement"
argument.

This new function is needed because sometimes we need to use the
replacement sha1.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -649,7 +649,11 @@ char *strip_path_suffix(const char *path, const char *suffix);
 
 /* Read and unpack a sha1 file into memory, write memory to a sha1 file */
 extern int sha1_object_info(const unsigned char *, unsigned long *);
-extern void * read_sha1_file(const unsigned char *sha1, enum object_type *type, unsigned long *size);
+extern void *read_sha1_file_repl(const unsigned char *sha1, enum object_type *type, unsigned long *size, const unsigned char **replacement);
+static inline void *read_sha1_file(const unsigned char *sha1, enum object_type *type, unsigned long *size)
+{
+	return read_sha1_file_repl(sha1, type, size, NULL);
+}
 extern int hash_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1);
 extern int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *return_sha1);
 extern int pretend_sha1_file(void *, unsigned long, enum object_type, unsigned char *);

sha1_file.c

@@ -2145,8 +2145,10 @@ static void *read_object(const unsigned char *sha1, enum object_type *type,
 	return read_packed_sha1(sha1, type, size);
 }
 
-void *read_sha1_file(const unsigned char *sha1, enum object_type *type,
-		     unsigned long *size)
+void *read_sha1_file_repl(const unsigned char *sha1,
+			  enum object_type *type,
+			  unsigned long *size,
+			  const unsigned char **replacement)
 {
 	const unsigned char *repl = lookup_replace_object(sha1);
 	void *data = read_object(repl, type, size);
@@ -2160,6 +2162,9 @@ void *read_sha1_file(const unsigned char *sha1, enum object_type *type,
 	if (!data && (has_loose_object(repl) || has_packed_and_bad(repl)))
 		die("object %s is corrupted", sha1_to_hex(repl));
 
+	if (replacement)
+		*replacement = repl;
+
 	return data;
 }