version: greatly simplify redo nonsense, now that we use VERSION.

Signed-off-by: David Anderson <danderson@tailscale.com>

version/version.xcconfig.do

@@ -1,5 +1,14 @@
-redo-ifchange mkversion.sh describe.txt extragitcommit.txt
-read -r describe <describe.txt
-read -r other <extragitcommit.txt
-ver=$(./mkversion.sh xcode "$describe" "$other")
-echo "$ver" >$3
+redo-ifchange version-info.sh
+
+. ./version-info.sh
+
+# CFBundleShortVersionString: the "short name" used in the App Store.
+# eg. 0.92.98
+echo "VERSION_NAME = $VERSION_SHORT"
+# CFBundleVersion: the build number. Needs to be 3 numeric sections
+# that increment for each release according to SemVer rules.
+#
+# We start counting at 100 because we submitted using raw build
+# numbers before, and Apple doesn't let you start over.  e.g. 0.98.3
+# -> 100.98.3
+echo "VERSION_ID = $VERSION_XCODE"