Merge branch 'bc/hash-independent-tests-part-6'

Test updates to prepare for SHA-2 transition continues.

* bc/hash-independent-tests-part-6:
  t4048: abstract away SHA-1-specific constants
  t4045: make hash-size independent
  t4044: update test to work with SHA-256
  t4039: abstract away SHA-1-specific constants
  t4038: abstract away SHA-1 specific constants
  t4034: abstract away SHA-1-specific constants
  t4027: make hash-size independent
  t4015: abstract away SHA-1-specific constants
  t4011: abstract away SHA-1-specific constants
  t4010: abstract away SHA-1-specific constants
  t3429: remove SHA1 annotation
  t1305: avoid comparing extensions
  rev-parse: add a --show-object-format option
  t/oid-info: add empty tree and empty blob values
  t/oid-info: allow looking up hash algorithm name

diff --cc builtin/rev-parse.c
Simple merge

diff --cc t/t3429-rebase-edit-todo.sh
Simple merge

diff --cc t/t4038-diff-combined.sh
index b9d876efa20469ae4cce824f9fd5924e13c936a1,15fc054fdb7e688316cb85ca08024ea691921daa..b5a56895e8e8368996c8c7f9314b4bf93fddd234
--- 1/t/t4038-diff-combined.sh
--- 2/t/t4038-diff-combined.sh
+++ b/t/t4038-diff-combined.sh
@@@ -507,9 -514,9 +514,9 @@@ test_expect_success FUNNYNAMES '--combi
  '
  
  test_expect_success FUNNYNAMES '--combined-all-paths and --raw -and -z and funny names' '
-       printf "aaf8087c3cbd4db8e185a2d074cf27c53cfb75d7\0::100644 100644 100644 f00c965d8307308469e537302baa73048488f162 088bd5d92c2a8e0203ca8e7e4c2a5c692f6ae3f7 333b9c62519f285e1854830ade0fe1ef1d40ee1b RR\0file\twith\ttabs\0i\tam\ttabbed\0fickle\tnaming\0" >expect &&
+       printf "$head\0::100644 100644 100644 $side1df $side2df $headf RR\0file\twith\ttabs\0i\tam\ttabbed\0fickle\tnaming\0" >expect &&
        git diff-tree -c -M --raw --combined-all-paths -z HEAD >actual &&
 -      test_cmp -a expect actual
 +      test_cmp expect actual
  '
  
  test_expect_success FUNNYNAMES '--combined-all-paths and --cc and funny names' '