Add jinja processing to alt command

With the new functionality, when the 'alt' command is called (or automatically
triggered), any file with a name ending in '##yadm_tmpl' is treated as a jinja
template. The template is processed by envtpl and the result is written to a
file without the '##yadm_tmpl' name. The variables passed into the template
processing are

  YADM_CLASS
  YADM_OS
  YADM_HOSTNAME
  YADM_USER

These variables are set according to the normal rules for
CLASS, OS, HOSTNAME, and USER during the alt processing.

yadm

@@ -114,30 +114,32 @@ function alt() {
 
   require_repo
 
-  match_class="$(config local.class)"
-  if [ -z "$match_class" ] ; then
+  local_class="$(config local.class)"
+  if [ -z "$local_class" ] ; then
     match_class="%"
+  else
+    match_class="$local_class"
   fi
   match_class="(%|$match_class)"
 
-  match_system="$(config local.os)"
-  if [ -z "$match_system" ] ; then
-    match_system=$(uname -s)
+  local_system="$(config local.os)"
+  if [ -z "$local_system" ] ; then
+    local_system=$(uname -s)
   fi
-  match_system="(%|$match_system)"
+  match_system="(%|$local_system)"
 
-  match_host="$(config local.host)"
-  if [ -z "$match_host" ] ; then
-    match_host=$(hostname)
-    match_host=${match_host%%.*} #; trim any domain from hostname
+  local_host="$(config local.host)"
+  if [ -z "$local_host" ] ; then
+    local_host=$(hostname)
+    local_host=${local_host%%.*} #; trim any domain from hostname
   fi
-  match_host="(%|$match_host)"
+  match_host="(%|$local_host)"
 
-  match_user="$(config local.user)"
-  if [ -z "$match_user" ] ; then
-    match_user=$(id -u -n)
+  local_user="$(config local.user)"
+  if [ -z "$local_user" ] ; then
+    local_user=$(id -u -n)
   fi
-  match_user="(%|$match_user)"
+  match_user="(%|$local_user)"
 
   #; regex for matching "<file>##CLASS.SYSTEM.HOSTNAME.USER"
   match1="^(.+)##(()|$match_system|$match_system\.$match_host|$match_system\.$match_host\.$match_user)$"
@@ -193,6 +195,30 @@ function alt() {
     done
   done
 
+  #; loop over all "tracked" files
+  #; for every file which is a *##yadm_tmpl create a real file
+  local IFS=$'\n'
+  local match="^(.+)##yadm_tmpl"
+  local envtpl_bin=$(which envtpl) 
+  for tracked_file in $("$GIT_PROGRAM" ls-files | sort) $(cat "$YADM_ENCRYPT" 2>/dev/null); do
+    tracked_file="$YADM_WORK/$tracked_file"
+    if [ -e "$tracked_file" ] ; then
+      if [[ $tracked_file =~ $match ]] ; then
+        if [[ -z "$envtpl_bin" ]]; then
+          debug "'envtpl' (pip install envtpl) not available, not creating $real_file from template $tracked_file"
+          [ -n "$loud" ] && echo "'envtpl' (pip install envtpl) not available, not creating $real_file from template $tracked_file"
+        else
+          real_file="${BASH_REMATCH[1]}"
+          debug "Creating $real_file from template $tracked_file"
+          [ -n "$loud" ] && echo "Creating $real_file from template $tracked_file"
+          YADM_CLASS="$local_class" YADM_OS="$local_system" \
+          YADM_HOSTNAME="$local_host" YADM_USER="$local_user" \
+          $envtpl_bin < $tracked_file > $real_file
+        fi
+      fi
+    fi
+  done
+
 }
 
 function bootstrap() {