Git version into info.plist. Add GenerateGFVersion.sh as a build step first in your build process.

GenerateGFVersion.sh

OUT=build/GFVersion.h

VERSION=`git describe | sed "y/-/./"`
SHORTVERSION=`echo $VERSION | cut -f 1-3 -d "."`

CONTENTS="#define GFVERSION $VERSION"$'\n'"#define GFSHORTVERSION $SHORTVERSION"
if [ -e $OUT ]
then
    EXISTING=`cat $OUT`
fi

if [ "$EXISTING" = "$CONTENTS" ]
then
    echo "Version unchanged"
    exit 0
fi

echo "Version changed"
mkdir -p build
echo "$CONTENTS" > $OUT

GFGetVersion.h

#import <Foundation/Foundation.h>

/// Retrieve version number of this library, roughly as outputted by git describe
extern NSString *GFGetVersion(void);

GFGetVersion.m

#import "GFGetVersion.h"
#import "../build/GFVersion.h"

#define REALSTR(x) #x
#define STR(x) REALSTR(x)

NSString *GFGetVersion(void)
{
	NSString *version = @STR(GFVERSION);
	return version;
}

Info.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>CFBundleDevelopmentRegion</key>
	<string>en</string>
	<key>CFBundleExecutable</key>
	<string>$(EXECUTABLE_NAME)</string>
	<key>CFBundleIconFile</key>
	<string></string>
	<key>CFBundleIdentifier</key>
	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
	<key>CFBundleInfoDictionaryVersion</key>
	<string>6.0</string>
	<key>CFBundleName</key>
	<string>$(PRODUCT_NAME)</string>
	<key>CFBundlePackageType</key>
	<string>APPL</string>
	<key>CFBundleShortVersionString</key>
	<string>GFSHORTAPPVERSION</string>  <---- NOTE HERE
	<key>CFBundleSignature</key>
	<string>????</string>
	<key>CFBundleVersion</key>
	<string>GFAPPVERSION</string>       <---- NOTE HERE
	<key>Fabric</key>
	<dict>
		<key>APIKey</key>
		<string>197595bba253e4e7b8a854885fe58d3bb2534ee4</string>
		<key>Kits</key>
		<array>
			<dict>
				<key>KitInfo</key>
				<dict/>
				<key>KitName</key>
				<string>Crashlytics</string>
			</dict>
		</array>
	</dict>
	<key>LSMinimumSystemVersion</key>
	<string>$(MACOSX_DEPLOYMENT_TARGET)</string>
	<key>NSAppTransportSecurity</key>
	<dict>
		<key>NSAllowsArbitraryLoads</key>
		<true/>
	</dict>
	<key>NSHumanReadableCopyright</key>
	<string>Copyright © 2015 Lookback. All rights reserved.</string>
	<key>NSMainNibFile</key>
	<string>MainMenu</string>
	<key>NSPrincipalClass</key>
	<string>NSApplication</string>
	<key>NSUserNotificationAlertStyle</key>
	<string>banner</string>
	<key>SUEnableAutomaticChecks</key>
	<true/>
	<key>SUFeedURL</key>
	<string>https://s3-eu-west-1.amazonaws.com/lookback-mac-releases/appcast.xml</string>
</dict>
</plist>

versioning.xcconfig

//:configuration = Debug
INFOPLIST_OTHER_PREPROCESSOR_FLAGS = -traditional
INFOPLIST_PREFIX_HEADER = $(SRCROOT)/build/GFAppVersion.h
INFOPLIST_PREPROCESS = YES

//:configuration = Release
INFOPLIST_OTHER_PREPROCESSOR_FLAGS = -traditional
INFOPLIST_PREFIX_HEADER = $(SRCROOT)/build/GFAppVersion.h
INFOPLIST_PREPROCESS = YES

//:completeSettings = some
INFOPLIST_OTHER_PREPROCESSOR_FLAGS
INFOPLIST_PREPROCESSOR_DEFINITIONS
INFOPLIST_PREFIX_HEADER
INFOPLIST_PREPROCESS