autoconf: use AC_CONFIG_COMMANDS instead of ad-hoc 'config.mak.append'

This will allow "./config.status --recheck; ./config.status" to work
correctly as a mean of reconfiguring the tree with the same configure
argument used in the previous "./configure" invocation.
Signed-off-by: NStefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

configure.ac

@@ -5,9 +5,22 @@
 
 # GIT_CONF_SUBST(VAL, VAR)
 # ------------------------
-# Append the line "VAR=VAL" to file ${config_append}
-AC_DEFUN([GIT_CONF_APPEND_LINE],
-         [echo "$1=$2" >> "${config_append}"])
+# Cause the line "VAR=VAL" to be eventually appended to ${config_file}.
+AC_DEFUN([GIT_CONF_SUBST],
+   [AC_REQUIRE([GIT_CONF_SUBST_INIT])
+   config_appended_defs="$config_appended_defs${newline}$1=$2"])
+
+# GIT_CONF_SUBST_INIT
+# -------------------
+# Prepare shell variables and autoconf machine required by later calls
+# to GIT_CONF_SUBST.
+AC_DEFUN([GIT_CONF_SUBST_INIT],
+    [config_appended_defs=; newline='
+'
+    AC_CONFIG_COMMANDS([$config_file],
+                       [echo "$config_appended_defs" >> "$config_file"],
+                       [config_file=$config_file
+                        config_appended_defs="$config_appended_defs"])])
 
 # GIT_ARG_SET_PATH(PROGRAM)
 # -------------------------
@@ -133,11 +146,8 @@ AC_INIT([git], [@@GIT_VERSION@@], [git@vger.kernel.org])
 AC_CONFIG_SRCDIR([git.c])
 
 config_file=config.mak.autogen
-config_append=config.mak.append
 config_in=config.mak.in
 
-echo "# ${config_append}.  Generated by configure." > "${config_append}"
-
 # Directories holding "saner" versions of common or POSIX binaries.
 AC_ARG_WITH([sane-tool-path],
   [AS_HELP_STRING(
@@ -1041,9 +1051,5 @@ AC_SUBST(PTHREAD_LIBS)
 AC_SUBST(NO_PTHREADS)
 
 ## Output files
-AC_CONFIG_FILES(["${config_file}":"${config_in}":"${config_append}"])
+AC_CONFIG_FILES(["${config_file}":"${config_in}"])
 AC_OUTPUT
-
-
-## Cleanup
-rm -f "${config_append}"