The result from "git diff" that compares two blobs, e.g. "git diff
$commit1:$path $commit2:$path", used to be shown with the full
object name as given on the command line, but it is more natural to
use the $path in the output and use it to look up .gitattributes.

* jk/diff-blob:
  diff: use blob path for blob/file diffs
  diff: use pending "path" if it is available
  diff: use the word "path" instead of "name" for blobs
  diff: pass whole pending entry in blobinfo
  handle_revision_arg: record paths for pending objects
  handle_revision_arg: record modes for "a..b" endpoints
  t4063: add tests of direct blob diffs
  get_sha1_with_context: dynamically allocate oc->path
  get_sha1_with_context: always initialize oc->symlink_path
  sha1_name: consistently refer to object_context as "oc"
  handle_revision_arg: add handle_dotdot() helper
  handle_revision_arg: hoist ".." check out of range parsing
  handle_revision_arg: stop using "dotdot" as a generic pointer
  handle_revision_arg: simplify commit reference lookups
  handle_revision_arg: reset "dotdot" consistently