Merge branch 'mh/mmap-packed-refs'

Operations that do not touch (majority of) packed refs have been
optimized by making accesses to packed-refs file lazy; we no longer
pre-parse everything, and an access to a single ref in the
packed-refs does not touch majority of irrelevant refs, either.

* mh/mmap-packed-refs: (21 commits)
  packed-backend.c: rename a bunch of things and update comments
  mmapped_ref_iterator: inline into `packed_ref_iterator`
  ref_cache: remove support for storing peeled values
  packed_ref_store: get rid of the `ref_cache` entirely
  ref_store: implement `refs_peel_ref()` generically
  packed_read_raw_ref(): read the reference from the mmapped buffer
  packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator`
  read_packed_refs(): ensure that references are ordered when read
  packed_ref_cache: keep the `packed-refs` file mmapped if possible
  packed-backend.c: reorder some definitions
  mmapped_ref_iterator_advance(): no peeled value for broken refs
  mmapped_ref_iterator: add iterator over a packed-refs file
  packed_ref_cache: remember the file-wide peeling state
  read_packed_refs(): read references with minimal copying
  read_packed_refs(): make parsing of the header line more robust
  read_packed_refs(): only check for a header at the top of the file
  read_packed_refs(): use mmap to read the `packed-refs` file
  die_unterminated_line(), die_invalid_line(): new functions
  packed_ref_cache: add a backlink to the associated `packed_ref_store`
  prefix_ref_iterator: break when we leave the prefix
  ...

1 files changed, 6 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index ed4ca438b..b143e4eea 100644
--- a/Makefile
+++ b/Makefile
@@ -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().
@@ -1391,6 +1394,9 @@ else
 		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