Move git tools from toktok-stack.

tools/git-co

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec git checkout "$@"

tools/git-d

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec git diff "$@"

tools/git-s

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec git status "$@"

tools/git-ss

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec git stack-status "$@"

tools/git-stack-status

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# Shows all the submodules that are not in their master branch, i.e. need to
+# have something merged before the stack PR can be merged.
+
+git submodule foreach --recursive --quiet \
+  'echo "$(git rev-parse --abbrev-ref HEAD): $path"' \
+  | grep -v master

tools/git-submit

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+set -eu
+
+BRANCH=$1
+
+git checkout "$BRANCH"
+git push upstream "$BRANCH:master"
+git checkout master
+git merge upstream/master
+git push
+git branch -d "$BRANCH"
+git push origin ":$BRANCH"