Add serve plugin.

Gives you access to two functions:
serve-html for serving a folder with whichever python version is
availabel and
serve-doc for serving a program’s documentation in /usr/share/doc.

plugins/serve/serve.plugin.zsh

@@ -0,0 +1,54 @@
+# Serves html documentation from /usr/share/doc and opens it in your browser
+# Args:
+#   doc_folder: folder in /usr/share/doc that should be served
+function serve-doc() {
+    local doc_base_path="/usr/share/doc"
+    local doc_folder=$1
+    local old_folder=$(pwd)
+
+    local folder="$doc_base_path/$doc_folder"
+    cd $folder || return
+    # look for an index file
+    if [ -e "$folder/index.html" ]; then
+        serve-html $folder
+    else
+        # look if there is one in /html
+        [ -e "$folder/html/index.html" ] \
+            && {cd $old_folder; serve-html "$folder/html"} \
+            || {echo "No documentation for that."; cd $old_folder >/dev/null}
+    fi
+}
+
+# Serves html from a folder and opens it in your browser
+# Args:
+#   folder: folder that should be served
+function serve-html() {
+    which python >/dev/null
+    if [ $? -ne 0 ]; then
+        echo "This function (serve-doc) uses Python. Please install it."
+        return
+    fi
+    local folder=$1
+    local old_folder=$(pwd)
+    cd $folder || return
+
+    # python2 prints --version to stderr, python3 to stdout
+    if [[ $(python --version 2>&1) =~ "Python 2.*" ]]; then
+        local invocation="python -m SimpleHTTPServer"
+    else
+        local invocation="python -m http.server"
+    fi
+
+    # This is not really equally distributed, but who cares
+    local port=$RANDOM
+    let "port %= 10000"
+    let "port += 50000"
+
+    # start server, put it in background
+    eval "$invocation $port >/dev/null" &
+    # open docs in browser
+    xdg-open "http://localhost:$port" &
+    cd $old_folder
+    # put server into foreground
+    fg; fg
+}