Merge branch 'jt/oidmap'

Introduce a new "oidmap" API and rewrite oidset to use it.

* jt/oidmap:
oidmap: map with OID as key

diff --combined Makefile
index b143e4eea3fa75eebd883361c40c3faa9e6c8060,64136dde488cacb317167b3363f6c2c9997fdc64..cd75985991f4535c45e2589222a9e6a38fb1d613
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -205,9 -205,6 +205,9 @@@ all:
  #
  # Define NO_MMAP if you want to avoid mmap.
  #
 +# Define MMAP_PREVENTS_DELETE if a file that is currently mmapped cannot be
 +# deleted or cannot be replaced using rename().
 +#
  # Define NO_SYS_POLL_H if you don't have sys/poll.h.
  #
  # Define NO_POLL if you do not have or don't want to use poll().
@@@ -824,6 -821,7 +824,7 @@@ LIB_OBJS += notes-cache.
  LIB_OBJS += notes-merge.o
  LIB_OBJS += notes-utils.o
  LIB_OBJS += object.o
+ LIB_OBJS += oidmap.o
  LIB_OBJS += oidset.o
  LIB_OBJS += packfile.o
  LIB_OBJS += pack-bitmap.o
@@@ -1394,9 -1392,6 +1395,9 @@@ els
                COMPAT_OBJS += compat/win32mmap.o
        endif
  endif
 +ifdef MMAP_PREVENTS_DELETE
 +      BASIC_CFLAGS += -DMMAP_PREVENTS_DELETE
 +endif
  ifdef OBJECT_CREATION_USES_RENAMES
        COMPAT_CFLAGS += -DOBJECT_CREATION_MODE=1
  endif