Fix most redownloading in 'vagrant reload --provision'.

Fixes #264.

provision.py

@@ -17,6 +17,7 @@ SUPPORTED_PLATFORMS = {
     ],
 }
 
+NPM_VERSION = '3.9.3'
 VENV_PATH = "/srv/zulip-venv"
 PY3_VENV_PATH = "/srv/zulip-py3-venv"
 ZULIP_PATH = os.path.dirname(os.path.abspath(__file__))
@@ -142,6 +143,7 @@ def main():
     run(["sudo", "apt-get", "update"])
     run(["sudo", "apt-get", "-y", "install"] + APT_DEPENDENCIES[codename])
 
+    if subprocess.call(['dpkg', '-s', TSEARCH_PACKAGE_NAME]):
         temp_deb_path = subprocess.check_output(["mktemp", "package_XXXXXX.deb", "--tmpdir"])
         run(["wget", "-O", temp_deb_path, TSEARCH_URL])
         run(["sudo", "dpkg", "--install", temp_deb_path])
@@ -187,8 +189,10 @@ def main():
     run(["tools/setup/postgres-init-test-db"])
     run(["tools/do-destroy-rebuild-test-database"])
     run(["python", "./manage.py", "compilemessages"])
-    # Install the latest npm.
-    run(["sudo", "npm", "install", "-g", "npm"])
+    if subprocess.check_output(['npm', '--version']).strip() != NPM_VERSION:
+        # Install the pinned version of npm.
+        run(["sudo", "npm", "install", "-g", "npm@{}".format(NPM_VERSION)])
+
     # Run npm install last because it can be flaky, and that way one
     # only needs to rerun `npm install` to fix the installation.
     run(["npm", "install"])

tools/setup/download-zxcvbn

@@ -2,5 +2,22 @@
 set -e
 set -x
 
-mkdir -p static/third/zxcvbn/
-wget https://raw.githubusercontent.com/dropbox/zxcvbn/0890678ede1488ecb02cda7eb793cd308a59c49d/zxcvbn.js -O static/third/zxcvbn/zxcvbn.js
+output_path=static/third/zxcvbn
+commit_file_path=$output_path/commit
+commit=0890678ede1488ecb02cda7eb793cd308a59c49d # Change this to upgrade
+
+mkdir -p "$output_path"
+
+if [ -e "$commit_file_path" ]
+then
+    current_commit=`cat $commit_file_path`
+else
+    current_commit=00
+fi
+
+if [ "$current_commit" == "$commit" ]; then
+    echo "Already at latest version of zxcvbn.js"
+else
+    echo "$commit" > "$commit_file_path"
+    wget "https://raw.githubusercontent.com/dropbox/zxcvbn/$commit/zxcvbn.js" -O "$output_path/zxcvbn.js"
+fi