This is an Xcode build script that will automatically change your app's Info.plist CFBundleVersion string to match the latest git tag for the working copy. If you have commits beyond the last tagged one, it will append a 'd' to the number.

GitTagBundleVersion.sh

#/bin/sh

INFO=$( echo $PWD )/MyApp-Info
TAG=$( git describe --tags `git rev-list --tags --max-count=1` )
COMMIT=
GITPATH=/usr/bin:/usr/local/bin:/usr/local/git/bin
PATH=$PATH:$GITPATH; export PATH

if [ -z $( which git ) ]; then
  echo "Unable to find git binary in \$GITPATH"
  exit 1
fi

# check if we've got untagged commits, adding a 'd' if so
if [ $( git log | sed -n '1p' | awk '{ print $2 }' ) != $( git rev-list --tags --max-count=1 ) ]; then
  TAG=$( echo $TAG )d
fi

CURRENT=$( defaults read "$INFO" CFBundleVersion )

if [ $CURRENT != $TAG ]; then
  # output for Xcode logging
  echo "Updating CFBundleVersion to $TAG"

  # write it to the Info.plist
  defaults write "$INFO" CFBundleVersion $TAG  
else
  # output for Xcode logging
  echo "CFBundleVersion already at $TAG"
fi

Why not use something like git describe to find the closest tag?

Good idea! I think mainly because git help didn't list it, so I wasn't aware of it! It solves both the "latest" issue as well as detecting commits past the last tag. Thanks!

git describe in general is a good format for showing the current build. If you don't like the fact that it gives a precise count from the latest tag, along with an abbreviated hash, you can use git describe --abbrev=0 to simply get the tag, and then test if that tag represents the current commit.