Makefile: Use computed header dependencies if the compiler supports it

diff --git a/Makefile b/Makefile
index 62ad0c2758ed3f464a61d7dc734f634ef43d8fc5..c131439a34a4d80e3c0ba35c13b2ccc53888538f 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -30,15 +30,15 @@ all::
 # Define LIBPCREDIR=/foo/bar if your libpcre header and library files are in
 # /foo/bar/include and /foo/bar/lib directories.
 #
-# Define NO_CURL if you do not have libcurl installed.  git-http-pull and
+# Define NO_CURL if you do not have libcurl installed.  git-http-fetch and
 # git-http-push are not built, and you cannot use http:// and https://
-# transports.
+# transports (neither smart nor dumb).
 #
 # Define CURLDIR=/foo/bar if your curl header and library files are in
 # /foo/bar/include and /foo/bar/lib directories.
 #
 # Define NO_EXPAT if you do not have expat installed.  git-http-push is
-# not built, and you cannot push using http:// and https:// transports.
+# not built, and you cannot push using http:// and https:// transports (dumb).
 #
 # Define EXPATDIR=/foo/bar if your expat header and library files are in
 # /foo/bar/include and /foo/bar/lib directories.
@@ -250,10 +250,6 @@ all::
 #   DEFAULT_EDITOR='$GIT_FALLBACK_EDITOR',
 #   DEFAULT_EDITOR='"C:\Program Files\Vim\gvim.exe" --nofork'
 #
-# Define COMPUTE_HEADER_DEPENDENCIES if your compiler supports the -MMD option
-# and you want to avoid rebuilding objects when an unrelated header file
-# changes.
-#
 # Define CHECK_HEADER_DEPENDENCIES to check for problems in the hard-coded
 # dependency rules.
 #
@@ -1236,6 +1232,15 @@ endif
 ifdef CHECK_HEADER_DEPENDENCIES
 COMPUTE_HEADER_DEPENDENCIES =
 USE_COMPUTED_HEADER_DEPENDENCIES =
+else
+ifndef COMPUTE_HEADER_DEPENDENCIES
+dep_check = $(shell sh -c \
+       '$(CC) -c -MF /dev/null -MMD -MP -x c /dev/null -o /dev/null 2>&1; \
+       echo $$?')
+ifeq ($(dep_check),0)
+COMPUTE_HEADER_DEPENDENCIES=YesPlease
+endif
+endif
 endif
 
 ifdef COMPUTE_HEADER_DEPENDENCIES
@@ -1876,7 +1881,7 @@ ifndef NO_CURL
        GIT_OBJS += http.o http-walker.o remote-curl.o
 endif
 XDIFF_OBJS = xdiff/xdiffi.o xdiff/xprepare.o xdiff/xutils.o xdiff/xemit.o \
-       xdiff/xmerge.o xdiff/xpatience.o
+       xdiff/xmerge.o xdiff/xpatience.o xdiff/xhistogram.o
 VCSSVN_OBJS = vcs-svn/string_pool.o vcs-svn/line_buffer.o \
        vcs-svn/repo_tree.o vcs-svn/fast_export.o vcs-svn/svndump.o
 VCSSVN_TEST_OBJS = test-obj-pool.o test-string-pool.o \