Merge branch 'js/find-lib-h-with-ls-files-when-possible'

The Makefile uses 'find' utility to enumerate all the *.h header
files, which is expensive on platforms with slow filesystems; it
now optionally uses "ls-files" if working within a repository,
which is a trick similar to how all sources are enumerated to run
ETAGS on.

* js/find-lib-h-with-ls-files-when-possible:
  Makefile: use `git ls-files` to list header files, if possible

Makefile

@@ -842,7 +842,8 @@ VCSSVN_LIB = vcs-svn/lib.a
 
 GENERATED_H += command-list.h
 
-LIB_H = $(shell $(FIND) . \
+LIB_H := $(shell git ls-files '*.h' ':!t/' ':!Documentation/' 2>/dev/null || \
+	$(FIND) . \
 	-name .git -prune -o \
 	-name t -prune -o \
 	-name Documentation -prune -o \
@@ -2376,7 +2377,7 @@ else
 # should _not_ be included here, since they are necessary even when
 # building an object for the first time.
 
-$(OBJECTS): $(LIB_H)
+$(OBJECTS): $(LIB_H) $(GENERATED_H)
 endif
 
 exec-cmd.sp exec-cmd.s exec-cmd.o: GIT-PREFIX