Build delta packs from the first build in the format

As an optimization to the client update experience, want to generate
deltas from the first build in the format to the currnet build.  This
will ensure that clients that are on old versions of Clear are able to
jump to the current build quickly.

Signed-off-by: George T Kramer <george.t.kramer@intel.com>

release/mixer.sh

@@ -80,20 +80,26 @@ build_update() {
 }
 
 build_deltas() {
+    local mix_format="${1}"
+
     section "Deltas"
 
-    log "Building delta packs..." 1
-    if (( NUM_DELTA_BUILDS > 0 )); then
-        sudo_mixer_cmd build delta-packs --previous-versions "${NUM_DELTA_BUILDS}"
+    local first_file="update/www/version/format${mix_format}/first"
+    if [[ -s "${first_file}" ]]; then
+        local first_version="$(< "${first_file}")"
+        log "Building deltas from the first build ${first_version} in format ${mix_format}..."
+        sudo_mixer_cmd build delta-packs --from "${first_version}"
+        sudo_mixer_cmd build delta-manifests --from "${first_version}"
     else
-        log "Skipping delta pack creation" "No positive number of build were specified"
+        log "Skipping delta creation from the first build ${first_version} in format ${mix_format}" "'first' file not found for format ${mix_format}"
     fi
 
-    log "Building delta manifests..."
     if (( NUM_DELTA_BUILDS > 0 )); then
+        log "Building deltas for the previous ${NUM_DELTA_BUILDS} builds..." 1
+        sudo_mixer_cmd build delta-packs --previous-versions "${NUM_DELTA_BUILDS}"
         sudo_mixer_cmd build delta-manifests --previous-versions "${NUM_DELTA_BUILDS}"
     else
-        log "Skipping delta manifest creation" "No positive number of builds were specified"
+        log "Skipping delta creation for the previous ${NUM_DELTA_BUILDS} builds" "'NUM_DELTA_BUILDS' <= 0"
     fi
 }
 
@@ -146,7 +152,7 @@ generate_bump() {
 
     build_update "${mix_ver}"
 
-    build_deltas
+    build_deltas "${mix_format}"
 
     # Bumped Build (+20)
     # Set the Mix Format
@@ -172,6 +178,7 @@ generate_bump() {
     MIN_VERSION=true build_update "${mix_ver_next}"
 
     echo -n "${mix_ver_next}" | sudo -E tee update/latest > /dev/null
+    echo -n "${mix_ver_next}" | sudo -E tee "update/www/version/format${mix_format_next}/first" > /dev/null
 }
 
 generate_mix() {
@@ -194,7 +201,7 @@ generate_mix() {
 
     build_update "${mix_ver}"
 
-    build_deltas
+    build_deltas "${mix_format}"
 
     echo -n "${mix_ver}" | sudo -E tee update/latest > /dev/null
 }