Merge branch 'jc/reflog'

* jc/reflog:
reflog --fix-stale: do not check the same trees and commits repeatedly.
reflog expire --fix-stale
Move traversal of reachable objects into a separate library.
builtin-prune: separate ref walking from reflog walking.
builtin-prune: make file-scope static struct to an argument.

diff --combined Makefile
index d2a838276099c65ec7a45b4abd40ce614456c1df,d8bfb6b87807d3b85ccacefc67edd40ac00642ea..6c12bc64ac9da2bb9fafd2a6a88053dc82b7d6d3
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -179,7 -179,7 +179,7 @@@ SCRIPT_SH = 
  SCRIPT_PERL = \
        git-add--interactive.perl \
        git-archimport.perl git-cvsimport.perl git-relink.perl \
 -      git-cvsserver.perl \
 +      git-cvsserver.perl git-remote.perl \
        git-svnimport.perl git-cvsexportcommit.perl \
        git-send-email.perl git-svn.perl
  
@@@ -210,7 -210,7 +210,7 @@@ EXTRA_PROGRAMS 
  
  BUILT_INS = \
        git-format-patch$X git-show$X git-whatchanged$X git-cherry$X \
 -      git-get-tar-commit-id$X \
 +      git-get-tar-commit-id$X git-init$X \
        $(patsubst builtin-%.o,git-%$X,$(BUILTIN_OBJS))
  
  # what 'all' will build and 'install' will install, in gitexecdir
@@@ -251,6 -251,7 +251,7 @@@ LIB_OBJS = 
        interpolate.o \
        lockfile.o \
        object.o pack-check.o patch-delta.o path.o pkt-line.o sideband.o \
+       reachable.o \
        quote.o read-cache.o refs.o run-command.o dir.o object-refs.o \
        server-info.o setup.o sha1_file.o sha1_name.o strbuf.o \
        tag.o tree.o usage.o config.o environment.o ctype.o copy.o \