Add ga-beacon analytics to gendocs scripts

hack/run-gendocs.sh puts ga-beacon analytics link into all md files,
hack/verify-gendocs.sh verifies presence of link.

hack/lib/util.sh

@@ -136,14 +136,21 @@ kube::util::gen-doc() {
   # create the list of generated files
   ls "${tmpdir}" | LC_ALL=C sort > "${tmpdir}/.files_generated"
 
-  # remove all old generated file from the destination
   while read file; do
+    # Add analytics link to generated .md files
+    if [[ "${file}" == *.md ]]; then
+      local link path
+      path=$(basename "$dest")/${file}
+      link=$(kube::util::analytics-link "${path}")
+      echo -e "\n${link}" >> "${tmpdir}/${file}"
+    fi
+    # remove all old generated files from the destination
     if [[ -e "${tmpdir}/${file}" && -n "${skipprefix}" ]]; then
       local original generated
       original=$(grep -v "^${skipprefix}" "${dest}/${file}") || :
       generated=$(grep -v "^${skipprefix}" "${tmpdir}/${file}") || :
       if [[ "${original}" == "${generated}" ]]; then
-        # overwrite generated with original.
+        # actual contents same, overwrite generated with original.
         mv "${dest}/${file}" "${tmpdir}/${file}"
       fi
     else
@@ -157,4 +164,44 @@ kube::util::gen-doc() {
   rm -rf "${tmpdir}"
 }
 
+# Takes a path $1 to traverse for md files to append the ga-beacon tracking
+# link to, if needed. If $2 is set, just print files that are missing
+# the link.
+kube::util::gen-analytics() {
+  local path="$1"
+  local dryrun="${2:-}"
+  local mdfiles dir link
+  # find has some strange inconsistencies between darwin/linux. The
+  # path to search must end in '/' for linux, but darwin will put an extra
+  # slash in results if there is a trailing '/'.
+  if [[ $( uname ) == 'Linux' ]]; then
+    dir="${path}/"
+  else
+    dir="${path}"
+  fi
+  # We don't touch files in Godeps|third_party, and the kubectl
+  # docs are autogenerated by gendocs.
+  mdfiles=($( find "${dir}" -name "*.md" -type f \
+              -not -path "${path}/Godeps/*" \
+              -not -path "${path}/third_party/*" \
+              -not -path "${path}/_output/*" \
+              -not -path "${path}/docs/kubectl*" ))
+  for f in "${mdfiles[@]}"; do
+    link=$(kube::util::analytics-link "${f#${path}/}")
+    if grep -q -F -x "${link}" "${f}"; then
+      continue
+    elif [[ -z "${dryrun}" ]]; then
+      echo -e "\n\n${link}" >> "${f}"
+    else
+      echo "$f"
+    fi
+  done
+}
+
+# Prints analytics link to append to a file at path $1.
+kube::util::analytics-link() {
+  local path="$1"
+  echo "[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/${path}?pixel)]()"
+}
+
 # ex: ts=2 sw=2 et filetype=sh