Enable directory caching

.travis.yml

@@ -1,4 +1,8 @@
 sudo: false
+cache:
+    directories:
+        - $HOME/.cache/pip
+        - tests/bot-ci
 addons:
     apt:
         packages:

tests/install.sh

@@ -1,6 +1,28 @@
 #!/bin/bash
-git clone --depth=1 git://github.com/powerline/bot-ci tests/bot-ci
+
-git clone --depth=1 git://github.com/powerline/deps tests/bot-ci/deps
+set -e
+
+remote_master_hex() {
+	local url="$1"
+	git ls-remote "$url" refs/heads/master | cut -f1
+}
+
+checkout_cached_dir() {
+	local url="$1"
+	local target="$2"
+	if ! test -e "$target/.version" || \
+		test "$(cat "$target/.version")" != "$(remote_master_hex "$url")" ; then
+		rm -rf "$target"
+	fi
+	if ! test -d "$target" ; then
+		git clone --depth=1 "$url" "$target"
+		mv "$target"/.git/refs/heads/master .version
+		rm -r "$target"/.git
+	fi
+}
+
+checkout_cached_dir git://github.com/powerline/bot-ci tests/bot-ci
+checkout_cached_dir git://github.com/powerline/deps tests/bot-ci/deps
 
 . tests/bot-ci/scripts/common/main.sh