autoconf: Use autoconf to write installation directories to config.mak.autogen

This is beginning of patch series introducing installation configuration
using autoconf (and no other autotools) to git. The idea is to generate
config.mak.autogen using ./configure (generated from configure.ac by running
autoconf) from config.mak.in, so one can use autoconf as an _alternative_ to
ordinary Makefile, and creating one's own config.mak. Local settings in
config.mak override generated settings in config.mak.autogen

This patch includes minimal configure.ac and config.mak.in, so one can set
installation directories using autoconf generated ./configure script
e.g. ./configure --prefix=/usr

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

.gitignore

@@ -135,4 +135,10 @@ git-core.spec
 *.[ao]
 *.py[co]
 config.mak
+autom4te.cache
+config.log
+config.status
+config.mak.in
+config.mak.autogen
+configure
 git-blame

INSTALL

@@ -13,6 +13,15 @@ that uses $prefix, the built results have some paths encoded,
 which are derived from $prefix, so "make all; make prefix=/usr
 install" would not work.
 
+Alternatively you can use autoconf generated ./configure script to
+set up install paths (via config.mak.autogen), so you can write instead
+
+	$ autoconf ;# as yourself if ./configure doesn't exist yet
+	$ ./configure --prefix=/usr ;# as yourself
+	$ make all doc ;# as yourself
+	# make install install-doc ;# as root
+
+
 Issues of note:
 
  - git normally installs a helper script wrapper called "git", which

Makefile

@@ -333,6 +333,7 @@ ifneq (,$(findstring arm,$(uname_M)))
 	ARM_SHA1 = YesPlease
 endif
 
+-include config.mak.autogen
 -include config.mak
 
 ifdef WITH_OWN_SUBPROCESS_PY

config.mak.in

@@ -0,0 +1,18 @@
+# git Makefile configuration, included in main Makefile
+# @configure_input@
+
+prefix = @prefix@
+exec_prefix = @exec_prefix@
+bindir = @bindir@
+#gitexecdir = @libexecdir@/git-core/
+template_dir = @datadir@/git-core/templates/
+GIT_PYTHON_DIR = @datadir@/git-core/python
+
+mandir=@mandir@
+
+srcdir = @srcdir@
+VPATH = @srcdir@
+
+export exec_prefix mandir
+export srcdir VPATH
+

configure.ac

@@ -0,0 +1,14 @@
+#                                               -*- Autoconf -*-
+# Process this file with autoconf to produce a configure script.
+
+AC_PREREQ(2.59)
+AC_INIT([git], [1.4.1], [git@vger.kernel.org])
+
+AC_CONFIG_SRCDIR([git.c])
+
+config_file=config.mak.autogen
+config_in=config.mak.in
+
+# Output files
+AC_CONFIG_FILES(["${config_file}":"${config_in}"])
+AC_OUTPUT