add --tag option that causes to build from the tagged tree. Will

currently use tagname in about box only if there are no uncommitted
local revisions.  git stash might fix this.  Also need either to use
user-friendly tag names or provide them as alternatives here.

xwords4/android/scripts/arelease.sh

@@ -1,7 +1,8 @@
 #!/bin/bash
 
 usage() {
-    echo "usage: $0 [<package-unsigned.apk>]" >&2
+    echo "Error: $*"
+    echo "usage: $0 [--tag <name>] [<package-unsigned.apk>]" >&2
     exit 1
 }
 
@@ -16,7 +17,29 @@ do_build() {
     cd $WD
 }
 
-FILES="$1"
+while [ -n "$1" ]; do
+    case $1 in
+        --tag) TAGNAME=$2
+            git describe $TAGNAME || usage "$TAGNAME not a valid git tag"
+            shift
+            ;;
+        *)
+            FILES="$1"
+            ;;
+    esac
+    shift
+done
+
+if [ -n "$TAGNAME" ]; then
+    git branch 2>/dev/null | grep '\* android_branch' \
+        || usage "not currently at android_branch"
+    git checkout $TAGNAME 2>/dev/null || usage "unable to checkout $TAGNAME"
+    HASH=$(git log -1 --pretty=format:%H)
+    CHECK_BRANCH=$(git describe $HASH 2>/dev/null)
+    if [ "$CHECK_BRANCH" != $TAGNAME ]; then
+        usage "tagname not found in repo or not as expected"
+    fi
+fi
 
 if [ -z "$FILES" ]; then
     do_build
@@ -39,3 +62,7 @@ for PACK_UNSIGNED in $FILES; do
     zipalign -v 4 $PACK_UNSIGNED $PACK_SIGNED
     [ -n "$XW_WWW_PATH" ] && cp $PACK_SIGNED $XW_WWW_PATH
 done
+
+if [ -n "$TAGNAME" ]; then
+    git checkout android_branch 2>/dev/null
+fi