Merge branch 'po/read-graft-line'

Conversion from uchar[20] to struct object_id continues; this is to
ensure that we do not assume sizeof(struct object_id) is the same
as the length of SHA-1 hash (or length of longest hash we support).

* po/read-graft-line:
commit: rewrite read_graft_line
commit: allocate array using object_id size
commit: replace the raw buffer with strbuf in read_graft_line
sha1_file: fix definition of null_sha1

diff --cc builtin/blame.c
Simple merge

diff --cc commit.h
Simple merge

diff --cc sha1_file.c
index f56bb5cae7ba5aed095bff90672b24c616cbcf54,f5b5bec52fd071029124dc69e6ba165b946f5a53..5f71bbac3ea9a11a4369ec0353e2e1258979ba19
--- 1/sha1_file.c
--- 2/sha1_file.c
+++ b/sha1_file.c
@@@ -28,9 -28,11 +28,9 @@@
  #include "list.h"
  #include "mergesort.h"
  #include "quote.h"
 -
 -#define SZ_FMT PRIuMAX
 -static inline uintmax_t sz_fmt(size_t s) { return s; }
 +#include "packfile.h"
  
- const unsigned char null_sha1[20];
+ const unsigned char null_sha1[GIT_MAX_RAWSZ];
  const struct object_id null_oid;
  const struct object_id empty_tree_oid = {
        EMPTY_TREE_SHA1_BIN_LITERAL