add script for managing build numbers

build_no.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env sh
+
+#
+# This script manages app build numbers.
+# It returns the next build number to be used.
+# If ran with --tag it will mark current HEAD with new build number.
+#
+# These numbers are used to mark app artifacts for:
+# * Play Store - versionCode attribute (gradle)
+# * Apple Store - CFBundleVersion attribute (plutil)
+#
+# The numbers need to be incremeneted and are maintained via
+# git tags matching the '^build-[0-9]+$' regex.
+# Builds from an already tagged commit should use the same number.
+#
+# For more details see:
+# * https://developer.android.com/studio/publish/versioning
+# * https://developer.apple.com/library/content/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
+# 
+
+getNumber () {
+    echo "$BUILD" | sed 's/[^0-9]*//g'
+}
+
+REGEX='^build-[0-9]\+$' 
+
+# check if current commit has a build tag
+BUILD=$(git tag --points-at refs/tags/HEAD | grep -e "$REGEX")
+
+# chech for multiple lines
+if [ 1 -lt $(echo "$BUILD" | grep -c -) ]; then
+    echo "Commit marked with one than one build tag!" >&2 
+    echo "$BUILD" >&2
+    exit 1
+fi
+
+# use already existing build number if applicable
+if [ -n "$BUILD" ]; then
+    echo "Current commit already tagged: $BUILD" >&2
+    getNumber $BUILD
+    exit 0
+fi
+
+# otherwise find the last used build number
+BUILD=$(git tag -l --sort=-v:refname | grep -e "$REGEX" | head -n 1)
+# extract the number
+BUILD_NO=$(getNumber "$BUILD")
+# increment
+BUILD_NO="$((BUILD_NO+1))"
+
+if [ "$1" = "--tag" ]; then
+    echo "Tagging refs/tags/HEAD: $BUILD" >&2
+    echo "You will need to 'git push --tags' to make this tag take effect." >&2
+    git tag "build-$BUILD_NO" refs/tags/HEAD
+fi
+
+# finally print build number
+echo "$BUILD_NO"