[PATCH] kbuild: automatically append a short string to the version based upon the git commit

If CONFIG_AUTO_LOCALVERSION is set, the user is using a git-based tree, and the
current HEAD is not referred to by any tags in .git/refs/tags/, append -g and
the first 8 characters of the commit to the version string.  This makes it
easier to use git-bisect, and/or to do a daily build, without trampling on your
older, working builds, or accidentally setting up conflicting sets of modules.

Signed-off-by: Ryan Anderson <ryan@michonline.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

3 files changed, 92 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index d01b004a2a0..c6aae86a02c 100644
--- a/Makefile
+++ b/Makefile
@@ -548,6 +548,26 @@ export KBUILD_IMAGE ?= vmlinux
 # images. Default is /boot, but you can set it to other values
 export	INSTALL_PATH ?= /boot
 
+# If CONFIG_LOCALVERSION_AUTO is set, we automatically perform some tests
+# and try to determine if the current source tree is a release tree, of any sort,
+# or if is a pure development tree.
+#
+# A 'release tree' is any tree with a git TAG associated
+# with it.  The primary goal of this is to make it safe for a native
+# git/CVS/SVN user to build a release tree (i.e, 2.6.9) and also to
+# continue developing against the current Linus tree, without having the Linus
+# tree overwrite the 2.6.9 tree when installed.
+#
+# Currently, only git is supported.
+# Other SCMs can edit scripts/setlocalversion and add the appropriate
+# checks as needed.
+
+
+ifdef CONFIG_LOCALVERSION_AUTO
+	localversion-auto := $(shell $(PERL) $(srctree)/scripts/setlocalversion $(srctree))
+	LOCALVERSION := $(LOCALVERSION)$(localversion-auto)
+endif
+
 #
 # INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
 # relocations required by build roots.  This is not defined in the
diff --git a/init/Kconfig b/init/Kconfig
index eb86972be1c..f27fc48c1fd 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -77,6 +77,22 @@ config LOCALVERSION
 	  object and source tree, in that order.  Your total string can
 	  be a maximum of 64 characters.
 
+config LOCALVERSION_AUTO
+	bool "Automatically append version information to the version string"
+	default y
+	help
+	  This will try to automatically determine if the current tree is a
+	  release tree by looking for git tags that
+	  belong to the current top of tree revision.
+
+	  A string of the format -gxxxxxxxx will be added to the localversion
+	  if a git based tree is found.  The string generated by this will be
+	  appended after any matching localversion* files, and after the value
+	  set in CONFIG_LOCALVERSION
+
+	  Note: This requires Perl, and a git repository, but not necessarily
+	  the git or cogito tools to be installed.
+
 config SWAP
 	bool "Support for paging of anonymous memory (swap)"
 	depends on MMU
diff --git a/scripts/setlocalversion b/scripts/setlocalversion
new file mode 100644
index 00000000000..7c805c8fccd
--- /dev/null
+++ b/scripts/setlocalversion
@@ -0,0 +1,56 @@
+#!/usr/bin/perl
+# Copyright 2004 - Ryan Anderson <ryan@michonline.com>  GPL v2
+
+use strict;
+use warnings;
+use Digest::MD5;
+require 5.006;
+
+if (@ARGV != 1) {
+	print <<EOT;
+Usage: setlocalversion <srctree>
+EOT
+	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);
+
+	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();
+}
+
+printf "-%s\n", join("-",@LOCALVERSIONS) if (scalar @LOCALVERSIONS > 0);