autoconf: Preparing the way for autodetection

Prepares configure.ac to output autodetected and selected (by using
--with/--without and --enable/disable parameters to generated
./configure script) building configuration in "git style", i.e. by
appending appropriate variables to output file config.mak.autogen
(via temporary file config.mak.append).

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

configure.ac

@@ -7,8 +7,19 @@ AC_INIT([git], [1.4.1], [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}"
+
+
+## Definitions of macros
+# GIT_CONF_APPEND_LINE(LINE)
+# --------------------------
+# Append LINE to file ${config_append}
+AC_DEFUN([GIT_CONF_APPEND_LINE],
+[echo "$1" >> "${config_append}"])# GIT_CONF_APPEND_LINE
+
 
 ## Checks for programs.
 # Define NO_PYTHON if you want to loose all benefits of the recursive merge.
@@ -121,6 +132,10 @@ config_in=config.mak.in
 # Define USE_STDEV below if you want git to care about the underlying device
 # change being considered an inode change from the update-cache perspective.
 
+
 ## Output files
-AC_CONFIG_FILES(["${config_file}":"${config_in}"])
+AC_CONFIG_FILES(["${config_file}":"${config_in}":"${config_append}"])
 AC_OUTPUT
+
+## Cleanup
+rm -f "${config_append}"