Slight improvement to the build script

Use `git log` instead of mixing `echo -n` and `git rev-parse`
Use `pushd/popd` for better CWD management

script/build

@@ -9,17 +9,16 @@ if [[ "$TRAVIS_PULL_REQUEST" =~ ^[0-9]+$ ]]; then
 fi
 
 
-for i in "$@"
-do
-  case $i in
+while [ $# -ne 0 ]; do
+  case $1 in
     --dev)
       DEV=YES
-      shift # past argument with no value
       ;;
     *)
       # unknown option
       ;;
   esac
+  shift
 done
 
 function force-fetch {
@@ -38,27 +37,24 @@ force-fetch smokey "https://github.com/Charcoal-SE/SmokeDetector.wiki" &
 wait
 
 for file in **/Home.md; do
-  mv "$file" "`dirname "$file"`/index.md"
+  mv "$file" "$(dirname "$file")/index.md"
 done
 
 ./add-front-matter.rb ms/** smokey/** &
 ./create-data-files.rb &
 wait
 
-echo -n "Theme commit: "
-git -C ./.tmp rev-parse HEAD
-echo -n "MS wiki commit: "
-git -C ./ms rev-parse HEAD
-echo -n "Smokey wiki commit: "
-git -C ./smokey rev-parse HEAD
+git -C ./.tmp   log -1 --pretty="Theme commit:       [%h] %s"
+git -C ./ms     log -1 --pretty="MS wiki commit:     [%h] %s"
+git -C ./smokey log -1 --pretty="Smokey wiki commit: [%h] %s"
 
 COMMIT_INFO="$(git log -1 --pretty="[%h] %B")"
 
 rm -r _site/assets # remove old assets
 
 export PAGES_ENV=dotcom # GitHub.com
 
-if [[ ! $DEV ]]; then
+if [ -z "$DEV" ]; then
   export JEKYLL_ENV=production
 
   bundle exec jekyll algolia push --trace &
@@ -68,8 +64,8 @@ else
   bundle exec jekyll build --incremental --profile --trace
 fi
 
-cd _site
-cd assets
+pushd _site # _site
+pushd assets # _site/assets
 mkdir -p css images
 
 for file in branding*.css; do
@@ -79,10 +75,12 @@ for file in charcoal*.png; do
   cp "$file" images/charcoal.png
 done
 
-cd ..
+popd # _site/assets
 
 if [[ ! $DEV ]]; then
   git add --all .
   git config --global push.default tracking
   ../push.sh -m "$COMMIT_INFO"
 fi
+
+popd # _site