Merge branch 'bc/object-id'

Conversion from uchar[20] to struct object_id continues.

* bc/object-id: (36 commits)
  convert: convert to struct object_id
  sha1_file: introduce a constant for max header length
  Convert lookup_replace_object to struct object_id
  sha1_file: convert read_sha1_file to struct object_id
  sha1_file: convert read_object_with_reference to object_id
  tree-walk: convert tree entry functions to object_id
  streaming: convert istream internals to struct object_id
  tree-walk: convert get_tree_entry_follow_symlinks internals to object_id
  builtin/notes: convert static functions to object_id
  builtin/fmt-merge-msg: convert remaining code to object_id
  sha1_file: convert sha1_object_info* to object_id
  Convert remaining callers of sha1_object_info_extended to object_id
  packfile: convert unpack_entry to struct object_id
  sha1_file: convert retry_bad_packed_offset to struct object_id
  sha1_file: convert assert_sha1_type to object_id
  builtin/mktree: convert to struct object_id
  streaming: convert open_istream to use struct object_id
  sha1_file: convert check_sha1_signature to struct object_id
  sha1_file: convert read_loose_object to use struct object_id
  builtin/index-pack: convert struct ref_delta_entry to object_id
  ...

strbuf.h

@@ -72,6 +72,12 @@ struct strbuf {
 extern char strbuf_slopbuf[];
 #define STRBUF_INIT  { .alloc = 0, .len = 0, .buf = strbuf_slopbuf }
 
+/*
+ * Predeclare this here, since cache.h includes this file before it defines the
+ * struct.
+ */
+struct object_id;
+
 /**
  * Life Cycle Functions
  * --------------------
@@ -558,7 +564,7 @@ extern void strbuf_list_free(struct strbuf **);
  * the strbuf `sb`.
  */
 extern void strbuf_add_unique_abbrev(struct strbuf *sb,
-				     const unsigned char *sha1,
+				     const struct object_id *oid,
 				     int abbrev_len);
 
 /**