move encode_in_pack_object_header() to a better place

Commit 1b22b6c897 made duplicated versions of encode_header() into a
common version called encode_in_pack_object_header(). There is however
a better location that sha1_file.c for such a function though, as
sha1_file.c contains nothing related to the creation of packs, and
it is quite populated already.

Also the comment that was moved to the header file should really remain
near the function as it covers implementation details and provides no
information about the actual function interface.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -911,14 +911,6 @@ extern void *unpack_entry(struct packed_git *, off_t, enum object_type *, unsign
 extern unsigned long unpack_object_header_buffer(const unsigned char *buf, unsigned long len, enum object_type *type, unsigned long *sizep);
 extern unsigned long get_size_from_delta(struct packed_git *, struct pack_window **, off_t);
 extern const char *packed_object_info_detail(struct packed_git *, off_t, unsigned long *, unsigned long *, unsigned int *, unsigned char *);
-/*
- * The per-object header is a pretty dense thing, which is
- *  - first byte: low four bits are "size", then three bits of "type",
- *    and the high bit is "size continues".
- *  - each byte afterwards: low seven bits are size continuation,
- *    with the high bit being "size continues"
- */
-int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr);
 
 /* Dumb servers support */
 extern int update_server_info(int);

pack-write.c

@@ -253,3 +253,30 @@ char *index_pack_lockfile(int ip_out)
 	}
 	return NULL;
 }
+
+/*
+ * The per-object header is a pretty dense thing, which is
+ *  - first byte: low four bits are "size", then three bits of "type",
+ *    and the high bit is "size continues".
+ *  - each byte afterwards: low seven bits are size continuation,
+ *    with the high bit being "size continues"
+ */
+int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
+{
+	int n = 1;
+	unsigned char c;
+
+	if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
+		die("bad type %d", type);
+
+	c = (type << 4) | (size & 15);
+	size >>= 4;
+	while (size) {
+		*hdr++ = c | 0x80;
+		c = size & 0x7f;
+		size >>= 7;
+		n++;
+	}
+	*hdr = c;
+	return n;
+}

pack.h

@@ -60,6 +60,7 @@ extern int check_pack_crc(struct packed_git *p, struct pack_window **w_curs, off
 extern int verify_pack(struct packed_git *);
 extern void fixup_pack_header_footer(int, unsigned char *, const char *, uint32_t, unsigned char *, off_t);
 extern char *index_pack_lockfile(int fd);
+extern int encode_in_pack_object_header(enum object_type, uintmax_t, unsigned char *);
 
 #define PH_ERROR_EOF		(-1)
 #define PH_ERROR_PACK_SIGNATURE	(-2)

sha1_file.c

@@ -1475,26 +1475,6 @@ const char *packed_object_info_detail(struct packed_git *p,
 	}
 }
 
-int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
-{
-	int n = 1;
-	unsigned char c;
-
-	if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
-		die("bad type %d", type);
-
-	c = (type << 4) | (size & 15);
-	size >>= 4;
-	while (size) {
-		*hdr++ = c | 0x80;
-		c = size & 0x7f;
-		size >>= 7;
-		n++;
-	}
-	*hdr = c;
-	return n;
-}
-
 static int packed_object_info(struct packed_git *p, off_t obj_offset,
 			      unsigned long *sizep)
 {