Mercurial Changeset Hash Build Script (iphone)

import os, subprocess, re, sys


appname = "yourappname"
hgbin = "/usr/local/bin/hg"
targetBuildDir = os.getenv("TARGET_BUILD_DIR")

getChangeset = subprocess.Popen(hgbin + ' parent --template "{node|short}" --cwd ' + targetBuildDir, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)

if (getChangeset.stderr.read() != ""):
	print "Error in obtaining current changeset of the Mercurial repository. '" + getChangeset.stderr.read() + "'"
	sys.exit(0)   # if you want the build to fail here since the changeset is malformed change this to sys.exit(1) 

changeset = getChangeset.stdout.read()
if (not re.search("^[0-9a-f]{12}$", changeset)):
	print "Current changeset of the Mercurial repository is malformed"
	sys.exit(0)   # if you want the build to fail here since the changeset is malformed change this to sys.exit(1) 

infoPlist = os.path.join(targetBuildDir, appname + ".app/Info.plist")
if  not os.path.exists(infoPlist):
	print "Cannot locate " + appname +".app/Info.plist"
	sys.exit(1)   # if you want the build to not fail here change this to sys.exit(0) 

result  = subprocess.Popen('/usr/libexec/PlistBuddy -c "Delete BuildHashKey" ' + infoPlist, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
result  = subprocess.Popen('/usr/libexec/PlistBuddy -c "Add BuildHashKey string '+ changeset + '" ' + infoPlist, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)

print appname + " BuildHashKey set to " + changeset

Source http://jasonfharris.com/blog/2010/05/versioning-your-application-with-the-mercurial-changeset-hash/