kbuild: Use git in scripts/setlocalversion

Currently scripts/setlocalversion is a Perl script that tries to figure
out the current git commit ID of a repo without using git.  It also
imports Digest::MD5 without using it and generally is too big for the
small task it does. :]  And it always reports a git ID, even when the
HEAD is tagged -- this is a bug.

This patch replaces it with a Bourne Shell script that uses git
commands to do the same.  I can't come up with a scenario where someone
would use a git repo and refuse to install git core at the same time,
so I think it's reasonable to assume git is available.

The new script also reports uncommitted changes by adding -git_dirty to
the version string.  Obviously you can't see from that _what_ has been
changed from the last commit, so it's more of a reminder that you
forgot to commit something.

The script is easily extensible: simply add a check for Mercurial (or
whatever) below the git check.

Note: the script doesn't print a newline char anymore.  That's only
because it was easier to implement it that way, not a feature (or bug).
'make kernelrelease' doesn't care.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Acked-by: Ryan Anderson <ryan@michonline.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/setlocalversion

-#!/usr/bin/perl
-# Copyright 2004 - Ryan Anderson <ryan@michonline.com>  GPL v2
+#!/bin/sh
+# Print additional version information for non-release trees.
 
-use strict;
-use warnings;
-use Digest::MD5;
-require 5.006;
-
-if (@ARGV != 1) {
-	print <<EOT;
-Usage: setlocalversion <srctree>
-EOT
-	exit(1);
+usage() {
+	echo "Usage: $0 [srctree]" >&2
+	exit 1
 }
 
-my ($srctree) = @ARGV;
-chdir($srctree);
-
-my @LOCALVERSIONS = ();
-
-# We are going to use the following commands to try and determine if this
-# repository is at a Version boundary (i.e, 2.6.10 vs 2.6.10 + some patches) We
-# currently assume that all meaningful version boundaries are marked by a tag.
-# We don't care what the tag is, just that something exists.
-
-# Git/Cogito store the top-of-tree "commit" in .git/HEAD
-# A list of known tags sits in .git/refs/tags/
-#
-# The simple trick here is to just compare the two of these, and if we get a
-# match, return nothing, otherwise, return a subset of the SHA-1 hash in
-# .git/HEAD
-
-sub do_git_checks {
-	open(H,"<.git/HEAD") or return;
-	my $head = <H>;
-	chomp $head;
-	close(H);
+cd "${1:-.}" || usage
 
-	opendir(D,".git/refs/tags") or return;
-	foreach my $tagfile (grep !/^\.{1,2}$/, readdir(D)) {
-		open(F,"<.git/refs/tags/" . $tagfile) or return;
-		my $tag = <F>;
-		chomp $tag;
-		close(F);
-		return if ($tag eq $head);
-	}
-	closedir(D);
-
-	push @LOCALVERSIONS, "g" . substr($head,0,8);
-}
-
-if ( -d ".git") {
-	do_git_checks();
-}
+# Check for git and a git repo.
+if head=`git rev-parse --verify HEAD 2>/dev/null`; then
+	# Do we have an untagged version?
+	if  [ "`git name-rev --tags HEAD`" = "HEAD undefined" ]; then
+		printf '%s%s' -g `echo "$head" | cut -c1-8`
+	fi
 
-printf "-%s\n", join("-",@LOCALVERSIONS) if (scalar @LOCALVERSIONS > 0);
+	# Are there uncommitted changes?
+	if git diff-files | read dummy; then
+		printf '%s' -git_dirty
+	fi
+fi