basic options parsing and whatnot.
diff --git a/git-subtree.sh b/git-subtree.sh
new file mode 100755
index 0000000..5e5b27f
--- /dev/null
+++ b/git-subtree.sh
@@ -0,0 +1,123 @@
+#!/bin/bash
+#
+# git-subtree.sh: split/join git repositories in subdirectories of this one
+#
+# Copyright (c) 2009 Avery Pennarun <apenwarr@gmail.com>
+#
+OPTS_SPEC="\
+git subtree split <revisions> -- <subdir>
+git subtree merge
+
+git subtree does foo and bar!
+--
+h,help show the help
+q quiet
+v verbose
+"
+eval $(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)
+. git-sh-setup
+require_work_tree
+
+quiet=
+command=
+
+debug()
+{
+ if [ -z "$quiet" ]; then
+ echo "$@" >&2
+ fi
+}
+
+#echo "Options: $*"
+
+while [ $# -gt 0 ]; do
+ opt="$1"
+ shift
+ case "$opt" in
+ -q) quiet=1 ;;
+ --) break ;;
+ esac
+done
+
+command="$1"
+shift
+case "$command" in
+ split|merge) ;;
+ *) die "Unknown command '$command'" ;;
+esac
+
+revs=$(git rev-parse --default HEAD --revs-only "$@") || exit $?
+dirs="$(git rev-parse --sq --no-revs --no-flags "$@")" || exit $?
+
+#echo "dirs is {$dirs}"
+eval $(echo set -- $dirs)
+if [ "$#" -ne 1 ]; then
+ die "Must provide exactly one subtree dir (got $#)"
+fi
+dir="$1"
+
+debug "command: {$command}"
+debug "quiet: {$quiet}"
+debug "revs: {$revs}"
+debug "dir: {$dir}"
+
+cache_setup()
+{
+ cachedir="$GIT_DIR/subtree-cache/$dir"
+ rm -rf "$cachedir" || die "Can't delete old cachedir: $cachedir"
+ mkdir -p "$cachedir" || die "Can't create new cachedir: $cachedir"
+ debug "Using cachedir: $cachedir" >&2
+ echo "$cachedir"
+}
+
+cache_get()
+{
+ for oldrev in $*; do
+ if [ -r "$cachedir/$oldrev" ]; then
+ read newrev <"$cachedir/$oldrev"
+ echo $newrev
+ fi
+ done
+}
+
+cache_set()
+{
+ oldrev="$1"
+ newrev="$2"
+ if [ -e "$cachedir/$oldrev" ]; then
+ die "cache for $oldrev already exists!"
+ fi
+ echo "$newrev" >"$cachedir/$oldrev"
+}
+
+cmd_split()
+{
+ debug "Splitting $dir..."
+ cache_setup || exit $?
+
+ git rev-list --reverse --parents $revs -- "$dir" |
+ while read rev parents; do
+ newparents=$(cache_get $parents)
+ echo "rev: $rev / $newparents"
+
+ git ls-tree $rev -- "$dir" |
+ while read mode type tree name; do
+ p=""
+ for parent in $newparents; do
+ p="$p -p $parent"
+ done
+ newrev=$(echo synthetic | git commit-tree $tree $p) \
+ || die "Can't create new commit for $rev / $tree"
+ cache_set $rev $newrev
+ done
+ done
+
+ exit 0
+}
+
+cmd_merge()
+{
+ die "merge command not implemented yet"
+}
+
+"cmd_$command"
