[PATCH 3/3] add autoupdate feature

[Jeff King <peff@peff.net>]

Users can't be bothered to keep their software up to date, so
we must do it for them.  Whenever any git command is
invoked, this patch checks for new releases of git at
kernel.org, and automatically upgrades your version of git.

Signed-off-by: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Sam Vilain <sam@vilain.net>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Nick Edelen <sirnot@gmail.com>
Signed-off-by: "J.H." <warthog9@kernel.org>
Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
---
 .gitignore          |    1 +
 Makefile            |    1 +
 git-autoupdate.perl |   58 +++++++++++++++++++++++++++++++++++++++++++++++++++
 git.c               |    9 +++++++-
 4 files changed, 68 insertions(+), 1 deletions(-)
 create mode 100644 git-autoupdate.perl

diff --git a/.gitignore b/.gitignore
index cf0d8b9..5a2703d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,6 +10,7 @@ git-annotate
 git-apply
 git-archimport
 git-archive
+git-autoupdate
 git-bisect
 git-bisect--helper
 git-blame
diff --git a/Makefile b/Makefile
index ae4b9fc..ba386a4 100644
--- a/Makefile
+++ b/Makefile
@@ -335,6 +335,7 @@ SCRIPT_SH += git-submodule.sh
 SCRIPT_SH += git-web--browse.sh
 
 SCRIPT_PERL += git-add--interactive.perl
+SCRIPT_PERL += git-autoupdate.perl
 SCRIPT_PERL += git-difftool.perl
 SCRIPT_PERL += git-archimport.perl
 SCRIPT_PERL += git-cvsexportcommit.perl
diff --git a/git-autoupdate.perl b/git-autoupdate.perl
new file mode 100644
index 0000000..c8ca10b
--- /dev/null
+++ b/git-autoupdate.perl
@@ -0,0 +1,58 @@
+#!/usr/bin/perl
+
+use LWP::Simple;
+use strict;
+
+my $ROOT = "http://kernel.org/pub/software/scm/git";
+
+my $us = our_git_version();
+my $them = latest_git_version();
+
+if (compare_versions($us, $them) < 0) {
+	print STDERR <<EOF;
+A new version of git is available! Auto-installing version $them.
+EOF
+}
+else {
+	exit 0;
+}
+
+upgrade($them);
+exit 42;
+
+sub our_git_version {
+	local $_ = `git version`;
+	/^git version (.*?)(\.\d+\.g[a-f0-9]+)?(\.dirty)?$/
+		or die "unable to read git version: $_";
+	return $1;
+}
+
+sub latest_git_version {
+	local $_ = get("$ROOT/");
+	my @versions = /git-([0-9.]+)\.tar\.gz/g
+		or die "unable to find any git versions at $ROOT";
+	# git version numbers have always sorted lexicographically so far,
+	# so let's just assume that will be the case forever
+	return (sort @versions)[-1];
+}
+
+sub compare_versions {
+	# let's assume lexicographical sorting again
+	return $_[0] cmp $_[1];
+}
+
+sub upgrade {
+	my $version = shift;
+	my $fn = "git-$version.tar.gz";
+	getstore("$ROOT/$fn", "/tmp/$fn") == 200
+		or die "unable to fetch $ROOT/$fn";
+	my $rc = system qq(
+		cd /tmp &&
+		gunzip -c $fn | tar xf - &&
+		cd git-$version &&
+		git config-mak >config.mak &&
+		make install
+	);
+	$rc == 0 or die "failed to upgrade git";
+	system("less /tmp/git-$version/RelNotes");
+}
diff --git a/git.c b/git.c
index 01ddf06..959ad52 100644
--- a/git.c
+++ b/git.c
@@ -462,10 +462,17 @@ int main(int argc, const char **argv)
 
 	if (!getenv("GIT_NOSPLASH") && !(argv[1] && !strcmp(argv[1], "splash"))) {
 		const char *a[] = { "splash", NULL };
-		const char *e[] = { "GIT_NOSPLASH=1", NULL };
+		const char *e[] = { "GIT_NOSPLASH=1", "GIT_NOAUTOUPDATE=1", NULL };
 		run_command_v_opt_cd_env(a, RUN_GIT_CMD, NULL, e);
 	}
 
+	if (!getenv("GIT_NOAUTOUPDATE")) {
+		const char *a[] = { "autoupdate", NULL };
+		const char *e[] = { "GIT_NOSPLASH=1", "GIT_NOAUTOUPDATE=1", NULL };
+		if (run_command_v_opt_cd_env(a, RUN_GIT_CMD, NULL, e) == 42)
+			exit(run_command_v_opt_cd_env(argv, 0, NULL, e));
+	}
+
 	/*
 	 * "git-xxxx" is the same as "git xxxx", but we obviously:
 	 *
-- 
1.6.5.1.3.g9d77a