Merge branch 'bc/hash-independent-tests'

Tests that rely on the exact hardcoded values of object names have
been updated in preparation for hash function migration.

* bc/hash-independent-tests:
  t2107: abstract away SHA-1-specific constants
  t2101: abstract away SHA-1-specific constants
  t2101: modernize test style
  t2020: abstract away SHA-1 specific constants
  t1507: abstract away SHA-1-specific constants
  t1411: abstract away SHA-1-specific constants
  t1405: sort reflog entries in a hash-independent way
  t1300: abstract away SHA-1-specific constants
  t1304: abstract away SHA-1-specific constants
  t1011: abstract away SHA-1-specific constants