Add 'generate-upgrade' command

To support OTP release upgrades I have added support for building
upgrade packages. Support for this is included in the
rebar_upgrade module, specifically generate_upgrade/2. It requires
one variable to be set on the command line 'previous_release' which
is the absolute path or relative path from 'rel/' to the previous
release one is upgrading from. Running an upgrade will create the
needed files, including a relup and result in a tarball containing
the upgrade being written to 'rel/'. When done it cleans up the
temporary files systools created.

Usage:
$ rebar generate-upgrade previous_release=/path/to/old/version

This also includes a dummy application that can be used to test
upgrades as well as an example.

Special thanks to Daniel Reverri, Jesper Louis Andersen and
Richard Jones for comments and patches.

1 files changed, 34 insertions, 0 deletions

diff --git a/test/upgrade_project/rel/files/erl b/test/upgrade_project/rel/files/erl
new file mode 100755
index 0000000..b985f23
--- /dev/null
+++ b/test/upgrade_project/rel/files/erl
@@ -0,0 +1,34 @@
+#!/bin/bash
+
+## This script replaces the default "erl" in erts-VSN/bin. This is necessary
+## as escript depends on erl and in turn, erl depends on having access to a
+## bootscript (start.boot). Note that this script is ONLY invoked as a side-effect
+## of running escript -- the embedded node bypasses erl and uses erlexec directly
+## (as it should).
+##
+## Note that this script makes the assumption that there is a start_clean.boot
+## file available in $ROOTDIR/release/VSN.
+
+# Determine the abspath of where this script is executing from.
+ERTS_BIN_DIR=$(cd ${0%/*} && pwd)
+
+# Now determine the root directory -- this script runs from erts-VSN/bin,
+# so we simply need to strip off two dirs from the end of the ERTS_BIN_DIR
+# path.
+ROOTDIR=${ERTS_BIN_DIR%/*/*}
+
+# Parse out release and erts info
+START_ERL=`cat $ROOTDIR/releases/start_erl.data`
+ERTS_VSN=${START_ERL% *}
+APP_VSN=${START_ERL#* }
+
+BINDIR=$ROOTDIR/erts-$ERTS_VSN/bin
+EMU=beam
+PROGNAME=`echo $0 | sed 's/.*\\///'`
+CMD="$BINDIR/erlexec"
+export EMU
+export ROOTDIR
+export BINDIR
+export PROGNAME
+
+exec $CMD -boot $ROOTDIR/releases/$APP_VSN/start_clean ${1+"$@"}