Merge branch 'np/delta'

* np/delta:
  builtin-pack-objects.c: avoid bogus gcc warnings
  threaded delta search: proper locking for cache accounting
  threaded delta search: add pack.threads config variable
  fix threaded delta search locking
  threaded delta search: specify number of threads at run time
  threaded delta search: better chunck split point
  threaded delta search: refine work allocation
  basic threaded delta search
  rearrange delta search progress reporting
  localize window memory usage accounting
  straighten the list of objects to deltify

Documentation/config.txt

@@ -630,9 +630,17 @@ pack.deltaCacheSize::
 	A value of 0 means no limit. Defaults to 0.
 
 pack.deltaCacheLimit::
-	The maxium size of a delta, that is cached in
+	The maximum size of a delta, that is cached in
 	gitlink:git-pack-objects[1]. Defaults to 1000.
 
+pack.threads::
+	Specifies the number of threads to spawn when searching for best
+	delta matches.  This requires that gitlink:git-pack-objects[1]
+	be compiled with pthreads otherwise this option is ignored with a
+	warning. This is meant to reduce packing time on multiprocessor
+	machines. The required amount of memory for the delta search window
+	is however multiplied by the number of threads.
+
 pull.octopus::
 	The default merge strategy to use when pulling multiple branches
 	at once.

Documentation/git-pack-objects.txt

@@ -169,6 +169,14 @@ base-name::
 	length, this option typically shrinks the resulting
 	packfile by 3-5 per-cent.
 
+--threads=<n>::
+	Specifies the number of threads to spawn when searching for best
+	delta matches.  This requires that pack-objects be compiled with
+	pthreads otherwise this option is ignored with a warning.
+	This is meant to reduce packing time on multiprocessor machines.
+	The required amount of memory for the delta search window is
+	however multiplied by the number of threads.
+
 --index-version=<version>[,<offset>]::
 	This is intended to be used by the test suite only. It allows
 	to force the version for the generated pack index, and to force

Makefile

@@ -124,6 +124,9 @@ all::
 # If not set it defaults to the bare 'wish'. If it is set to the empty
 # string then NO_TCLTK will be forced (this is used by configure script).
 #
+# Define THREADED_DELTA_SEARCH if you have pthreads and wish to exploit
+# parallel delta searching when packing objects.
+#
 
 GIT-VERSION-FILE: .FORCE-GIT-VERSION-FILE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -675,6 +678,11 @@ ifdef NO_MEMMEM
 	COMPAT_OBJS += compat/memmem.o
 endif
 
+ifdef THREADED_DELTA_SEARCH
+	BASIC_CFLAGS += -DTHREADED_DELTA_SEARCH
+	EXTLIBS += -lpthread
+endif
+
 ifeq ($(TCLTK_PATH),)
 NO_TCLTK=NoThanks
 endif