pip: successfully cache all the packages

Switch to using curl and regular expressions to generate a local cache
file so that we don't need to hit pypi.python.org every time.
This (obviously) results in a massive speed improvement, especially if
you spawn new shells frequently.

This also makes the autocompletion work for me, it didn't before. (pip
would always time out.)

And, also, for fun: This allows you to explicitly set which pip indexes
to use. Technically the old version of the plugin should have had this
behavior automatically -- without having to do more than configure pip
-- but the install completion never worked for me so this is a net gain
in functionality.

plugins/pip/_pip

@@ -6,8 +6,8 @@
 _pip_all() {
   # we cache the list of packages (originally from the macports plugin)
   if (( ! $+piplist )); then
-      echo -n " (caching package index...)"
-      piplist=($(pip search * | cut -d ' ' -f 1 | tr '[A-Z]' '[a-z]'))
+      zsh-pip-cache-packages
+      piplist=($(cat $ZSH_PIP_CACHE_FILE))
   fi
 }
 

plugins/pip/pip.plugin.zsh

@@ -0,0 +1,37 @@
+# Usage:
+# Just add pip to your installed plugins.
+
+# If you would like to change the cheeseshops used for autocomplete set
+# ZSH_PIP_INDEXES in your zshrc. If one of your indexes are bogus you won't get
+# any kind of error message, pip will just not autocomplete from them. Double
+# check!
+#
+# If you would like to clear your cache, go ahead and do a
+# "zsh-pip-clear-cache".
+
+ZSH_PIP_CACHE_FILE=~/.pip/zsh-cache
+ZSH_PIP_INDEXES=(https://pypi.python.org/simple/)
+
+zsh-pip-clear-cache() {
+  rm $ZSH_PIP_CACHE_FILE
+  unset piplist
+}
+
+zsh-pip-cache-packages() {
+  if [[ ! -d ${PIP_CACHE_FILE:h} ]]; then
+      mkdir -p ${PIP_CACHE_FILE:h}
+  fi
+
+  if [[ ! -f $ZSH_PIP_CACHE_FILE ]]; then
+      echo -n "(...caching package index...)"
+      tmp_cache=/tmp/zsh_tmp_cache
+      for index in $ZSH_PIP_INDEXES ; do
+          # well... I've already got two problems
+          curl $index 2>/dev/null | \
+              sed -nr '/^<a href/ s/.*>([^<]+).*/\1/p' \
+               >> $tmp_cache
+      done
+      sort $tmp_cache | uniq | tr '\n' ' ' > $ZSH_PIP_CACHE_FILE
+      rm $tmp_cache
+  fi
+}