Merge branch 'sb/hashmap-cleanup'

Merge branch 'sb/hashmap-cleanup'

Many uses of comparision callback function the hashmap API uses
cast the callback function type when registering it to
hashmap_init(), which defeats the compile time type checking when
the callback interface changes (e.g. gaining more parameters).
The callback implementations have been updated to take "void *"
pointers and cast them to the type they expect instead.

* sb/hashmap-cleanup:
  t/helper/test-hashmap: use custom data instead of duplicate cmp functions
  name-hash.c: drop hashmap_cmp_fn cast
  submodule-config.c: drop hashmap_cmp_fn cast
  remote.c: drop hashmap_cmp_fn cast
  patch-ids.c: drop hashmap_cmp_fn cast
  convert/sub-process: drop cast to hashmap_cmp_fn
  config.c: drop hashmap_cmp_fn cast
  builtin/describe: drop hashmap_cmp_fn cast
  builtin/difftool.c: drop hashmap_cmp_fn cast
  attr.c: drop hashmap_cmp_fn cast