Thursday, 26 January 2017

Semantic Versioning with Powershell, TeamCity and GitHub

Here at Spotlight Towers, we’ve been using TeamCity as our main build server since version 6; it’s a fantastic tool and we love it dearly. It got even better a few years back when we paired it with the marvellous Octopus Deploy; TeamCity builds the code and creates a set of deployable packages known as Octopacks; Octopus deploys the packages, and everything works quite nicely. Well, almost everything. One of the few problems that TeamCity + Octopus doesn’t magically solve for us is versioning. In this post, we’re going to look at how we use Git and TeamCity to manage versioning for our individual packages.

If this sounds like your sort of thing, why not come and work for us? That’s right – Spotlight is hiring! We're looking for developers, testers and a new UX/Web designer - check out and get in touch if you’re interested.

First, let’s establish some principles

  • We are going to respect the semantic versioning convention of MAJOR.MINOR.PATCH, as described at
  • Major and minor versions will be incremented manually. We trust developers to know whether their latest commit should be a new major or minor release according to semantic versioning principles.
  • Building the same codebase from the same branch twice should produce the same semantic version number.
  • Packages created from the master branch are release packages.
  • Packages created from a merge head of an open pull request are pre-release packages.
  • Pre-release packages will use the version number that would be assigned if that branch was accepted for release at build time.

Now, here’s the part where we’re going to deviate from the semantic versioning specification, because our packages actually use a four-part version number. We want to include a build number in our package versions, but the official semver extension for doing this – MAJOR.MINOR.PATCH+BUILD - won’t work with NuGet, so we’re going to use a four-part version number MAJOR.MINOR.PATCH.BUILD. Pre-release packages will be appended with a suffix describing which branch they were built from – MAJOR.MINOR.PATCH.BUILD-BRANCH.

OK, here’s an illustrated example that demonstrates what we’re trying to achieve. Master branch is green. Two developers are working on feature branches – blue and red in this example. To create our pre-release builds, we’re using a little-documented but incredibly useful feature of GitHub known as ‘merge heads’. The idea is that if you have an open pull request, the merge head will give you a snapshot of the codebase that would be created by merging the open pull request into master – so you’re not just testing your new feature in isolation, you’re actually building and testing your new feature plus the current state of the master branch. There is one caveat to this, which I’ll explain below.

So, we’ve got TeamCity set up to build and publish packages every time there’s a commit to master or to the merge head of an open pull request, and we’re also occasionally triggering manual builds just to make sure everything’s hanging together properly. Here’s what happens: 

semantic merging 500px

That line there that’s highlighted in yellow is a gotcha. At this point in our workflow, we’ve merged PR1 into our master branch, but because we haven’t pushed anything to the blue branch since this happened, the blue merge head is out of date. PR2 does NOT reflect the latest changes to master, and if we trigger a build manually, we’ll end up with a package that doesn’t actually reflect the latest state of the codebase. The workaround is pretty simple; if you’re creating pre-release builds from merge heads, never run these builds manually; make sure you always trigger the build by pushing a change to the branch.

Now let’s look at how can we get TeamCity to automatically calculate those semantic version numbers whenever a build is triggered. We’ll start with the major and minor version. We’re going to track these by creating a version.txt file in the root of the project codebase, which just contains the major and minor version numbers. If a developer decides that their feature branch represents a new major or minor version, it’s their responsibility to edit version.txt as part of implementing the feature. This also means that prerelease packages built from that branch will reflect the new version number whilst master branches will continue to use the old version until the branch gets merged, which I think is rather elegant.

For the patch version, we’re going to assume that every commit or merge to the master branch represents a new patch version, according to the following algorithm

  • If the current version.txt represents a NEW major/minor version, the patch number is zero
  • Otherwise, the patch number is the patch number of the latest release, incremented by the number of commits to the master branch since that release.

So – how do we know how many commits there have been since the last release? First, each time we build a release branch, we’re going to use Git tags to tag the repository with the version number we’ve just built. TeamCity will do this for you automatically using a build feature called “VCS labeling”:


Assuming every release has a corresponding tag, now we need to find the most recent release number, which we can do from the Git command line.

git fetch –tags
git tag –sort=v:refname

Git tags aren’t retrieved by default, so we need to explicitly fetch them before listing them. Then we list all the tags, specifying sort=v:refname which causes tag names to be treated as semantic versions when sorting. (Remember that semver sorting isn’t alphanumeric – in alphanumerics, v9 is higher than v12). Once we’ve got the latest tag, we need to count the number of revisions since that tag was created, which we can do using this syntax:

git rev-list v1.2.3..HEAD –count

To use this in our TeamCity build, we'll need to output the various different formats of that version so that TeamCity can use them. We want to do three things here:

  • Label the VCS root with the three-part semantic version number v1.2.3
  • Update the AssemblyInfo.cs files with the four-part version number – note that we can’t put any prerelease suffix in the AssemblyInfo version.
  • Pass the full version – – to Octopack when creating our deployable packages with Octopus.

I've wrapped the whole thing up in a Powershell script which runs as part of the TeamCity build process, which is on GitHub:

To use it in your project, add versions.ps1 to the root of your project repo; create a text file called version.txt which contains your major.minor version, and then add a TeamCity build step at the beginning of your build process that looks like this:


Finally, it’s worth mentioning that to use command-line git from Powershell, I had to set up TeamCity to use an SSH VCS root rather than HTTP, and install the appropriate SSH keys on the TeamCity build agent. I don't know whether this is a genuine requirement or a quirk of our configuration; your mileage may vary. And I still find Powershell infuriatingly idiosyncratic, but hey - you probably knew that already. :)

Happy versioning! And like I said, if this sort of thing sounds like something you’d like to work on, awesome - we’re hiring! Check out for more details and get in touch if you’re interested.

Monday, 9 January 2017

Sharing a Dropbox folder using Bootcamp and exFAT

My main laptop for the last few years has been a 15” Retina MacBook Pro. As I’m primarily a .NET developer, I use Bootcamp to run Windows 10, Visual Studio and SQL Server, but I also boot into macOS almost daily for things like audio recording and video editing using Logic Pro and Adobe Premiere. I’m also a huge fan of Dropbox – I use Evernote for text documents (notes, talk ideas and lyrics), and Dropbox for just about everything else.

My MacBook Pro has a 500Gb SSD, which sounds like a lot, but once you’ve got two operating systems it’s surprising how quickly you start running out of space – and one of my biggest frustrations was having two separate Dropbox folders. I have about 40Gb of stuff in Dropbox, which means a 40Gb Dropbox folder on my NTFS Windows partition, and another 4Gb Dropbox folder on the ExtFS macOS partition. And they store exactly the same filesso much so that Dropbox actually became my default sync mechanism for getting files from Windows into macOS and vice versa.

Being a huge nerd, I thought it would be fun to kick off 2017 by completely repaving my laptop, and I wondered if there was some way to store my Dropbox folder, and other big things like my music library, on a shared partition that both operating systems could use. It took a bit of tweaking but I think I’ve managed to get it working – here’s how. The secret sauce that made it all work is a relatively new file system called exFAT. The killer feature of exFAT here is that both Windows 10 and macOS can read and write it natively, but it doesn’t have any of the file size or volume size restrictions of older interoperable formats like FAT32.

Caveat: this is all completely unsupported. If you try any of this and you lose all your files, I’m not going to help you – and neither are Apple, Microsoft or Dropbox. If you’re happy using batch scripts to toggle file attributes and manually partitioning your OS drive, then this lot might help – but messing around with disk partitions and unsupported filesystems is a good way to end up with an unbootable laptop and a lot of bad mojo. So before we go any further,  back up everything. After all, Dropbox is a file sync tool – if some bizarre combination of macOS and exFAT results in it removing a load of files, the last thing I want is for Dropbox to conveniently remove the same files from all my other devices. I know it’s easy enough to revert to an older version of anything that’s in Dropbox, but I figured having a copy of it all on an external HD probably couldn’t hurt.

Next, work out how you want to partition your disk. In my case, I wanted to go for a ~150Gb partition for each operating system, and a 200Gb shared partition that both of them could see. Your mileage may vary, and – as I did – you might find you can’t get exactly what you wanted, but I managed to get pretty close. Now do a completely clean reinstall of macOS. Give it the entire drive and let it do its thing. Once you’re done, use the Boot Camp Assistant to set up and install Windows. When Boot Camp Assistant asks how you’d like to partition your drive, make the Windows partition equivalent to the total size of your desired Windows partition plus your shared partition – so in this case, I temporarily had a 150Gb macOS partition and a 350Gb Windows partition.

Screen Shot 2017-01-07 at 13.06.39

Once you’ve partitioned the disk, install Windows as usual. You should end up with a regular Boot Camp system, that you can boot into macOS or Windows by holding down the alt key during system startup or by using the Boot Camp options in Windows. Now here’s the fun part. Once you’ve installed Windows, but before you install any other apps or files, you’re going to use the Windows disk utility to shrink that Windows partition down to 150Gb and then create a shared exFAT partition in the remaining space. Right-click the BOOTCAMP (C:) partition, click Shrink Volume...


There’s some limit of the NTFS filesystem that means “you cannot shrink a volume beyond the point where any unmovable files are located”. Now I don’t know how much variance there is between Windows installations, but I couldn’t shrink my C: drive any smaller than 163Gb, despite the fact that the fresh Windows install only took up about 20Gb. For what I needed, this was close enough – if not, I’d have been looking for something that would let me defrag and reorganize the NTFS partition. Or reading up on how an SSD gets fragmented in the first place – I thought they were just big boxes of non-volatile solid-state memory?

Anyway. Next step was to format the new partition as exFAT, called it Shared, and then reboot into macOS and make sure it was visible. I poked around a bit, created some text documents and other files, rebooted back into Windows… After an hour or so this all seemed to be working quite nicely. Next step was to see how Dropbox coped with it. Rather than throw it at my 40Gb Dropbox account, I set up a new Dropbox account, installed Dropbox on both macOS and Windows and signed into to both of them using the new account.

This is where things got a bit weird. Here’s my best hypothesis as to what’s happening.

  1. macOS is storing some additional metadata for every file. On a regular ExtFS filesystem, the metadata is stored somewhere in the filesystem itself. On an exFAT partition, it’s stored in a tiny hidden file (apparently known as an AppleDouble) next to the original. Alongside foo.txt there’s now a 4k file called ._foo.txt. I don’t think this is a Dropbox thing, it just appears to be caused by running macOS on a non-ExtFS drive.
  2. The Dropbox agent on macOS sees these extra files, thinks that they’re important, and uploads them to Dropbox.
  3. The dot-underscore ._ files are then synced across all your other Dropbox devices – I can see them in the web interface as well as on my Windows partition.

If I wasn’t using Dropbox, the ._ files would still be there, but macOS marks them as hidden and Windows appears to respect this – doing a dir /a:h in one of my exFAT folders will show them but by default they don’t appear in Windows Explorer. I figured this wasn’t a big deal – I could live with a bunch of hidden 4K files – so I removed the temporary Dropbox account and installed the real one. This may have been a bit overly optimistic. Dropbox happily synced 40Gb of files from Windows, but when I rebooted into macOS, it created the ._ files for all of them… and then when I rebooted into Windows again, it started trying to sync all the hidden ._ files. After twelve hours of this, I concluded that something wasn’t working quite as I’d hoped, so I modified the plan slightly.

I realized that I don’t actually need the Dropbox agent running on both OSes – just having the shared Dropbox folder is enough – so I uninstalled the Dropbox agent from macOS, and things suddenly got a lot more straightforward. The dot-underscore files are still there. On the exFAT shared partition they’re hidden by default, but Dropbox helpfully syncs all the ._ files into all my other Windows systems and so I’ve created  a batch script in my Dropbox folder that finds any of these and sets them to hidden so they don’t show up in Windows Explorer. It’s a one-liner:

for /r %1 in (._*) do attrib +h "%1"

The last thing I wanted to try before doing it for real was to see how VMWare Fusion coped with the shared partition. As well as dual-booting between macOS and Windows, I’ll also occasionally use VMWare to run the Windows partition as a VM inside macOS, which works pretty well. Here’s what I discovered:

  • As soon as you boot the Windows VM, both the BOOTCAMP partion and the Shared partition disappear from macOS.
  • The BOOTCAMP partition is mounted in VMWare as drive C: (obviously), and the Shared partition appears in the VM as drive D:
  • The Dropbox agent will immediately pick up and sync any files created from macOS
  • When I shut down the VM, the BOOTCAMP and Shared partitions both show up in macOS again and everything’s back to normal.

So, here’s the final setup I ended up with. Windows 10 is running the Dropbox agent, and syncing files with my Dropbox cloud storage as intended. The Dropbox folder is on the shared exFAT partition, so macOS can read and write my local Dropbox folder, but macOS doesn’t sync anything. If I add files to Dropbox when running macOS, when I reboot into Windows again, the sync agent will pick up these new files and sync them to the cloud. Finally, if I’m in macOS and find I need a file that’s been added to Dropbox from another device and hasn’t synced yet, I can either reboot into Windows and sync it, fire up the VMWare machine for a few moments, or just download it via the web interface.

I've been running it for a couple of weeks, including a week of wrangling PowerPoint slides and shared files at NDC London, and it's working really quite nicely. And it's really rather nice to have nearly 200Gb of free disk space after installing both operating systems, all my apps and utilities, and 40Gb worth of Dropbox files.

Tuesday, 3 January 2017

My Life with the Microsoft Natural Keyboard

A moment ago I was catching up on Twitter and I saw this:

Now Scott has written some great posts about keyboards – and mice, and workstation ergonomics in general – over the years, so I immediately clicked the link to see what was so exciting… and wow. This is the new Microsoft Surface Ergonomic Keyboard, and I, too, am now sitting here trying not to buy it. Actually, I’m waiting for a UK layout, and then I suspect that trying not to buy it will rapidly become unmanageable. I may even fail to not buy two of them so I have one at work and one at home.

Top view of keyboard

Now, there’s a couple of things about this keyboard that are interesting only because Microsoft have consistently got them right, and then messed them up, and then got them right again, and then messed them up again - over many, many years. Like an even-numbered Star Trek movie or an odd-numbered version of CorelDraw, this latest one is a good one – and as somebody who’s used every incarnation of the Microsoft Natural keyboard, this seems like a nice opportunity to take a little wander down memory lane.

OK, cue the Wayne’s World dream-sequence time-travel effects… and here’s a keyboard. A 102-key IBM PS/2 keyboard, which was the standard layout for PC keyboards for about a decade, back in the days when keyboards were beige and the cool kids knew all sorts of tricks that would let you load HIMEM.SYS and your mouse driver and still have enough main memory left to run Wing Commander 2.

IBM Model M.png(IBM PS/2 keyboard by Raymangold22 via Wikipedia | CC0 | Link)

Around the time of Windows 95, Microsoft proposed the subtle addition of a two new keys – a Windows key (actually two of them) in those handy gaps next to the Ctrl keys, and a key that I’ve just this second learned is called the menu key, which is basically a right-click key. Other than shortening the space bar slightly, these new keys didn’t really move things around much, which was great, because that hard-earned muscle memory that let you hit triple-key combinations without taking your eyes off the screen worked just fine.

Oh, and they also started making them in colours that weren’t beige, which was a big improvement if you actually had to share your living space with them.


It’s around this time that I left school and got my first IT job, which meant I was typing for a good chunk of every day, and within a year I started getting unpleasant pain in my wrists and forearms. During a chance conversation at work, someone mentioned that a former employee there had had the same problem and switched to using an ergonomic keyboard – which was still knocking around in a cupboard somewhere. I tried it out and was instantly smitten.

This was the original Microsoft Natural keyboard, released in 1994.

imagePhoto by DeanW77 via Wikipedia – own work, CC BY-SA 4.0, Link

I absolutely loved it. I literally wore it out – I used it until some of the keys no longer worked, and then went shopping for a replacement… and discovered you couldn’t get the original Natural keyboard anymore; it had been replaced by the Natural Keyboard Elite, released in 1998. 

Looks close enough, right? Except if you look closely, you’ll see that instead of the familiar inverted-T cursor shape and two rows of navigation keys, the cursor keys are in a sort of weird diamond formation and the navigation keys are in two columns.

This was horrible. All those years of muscle memory suddenly gone – every time you’d try to hit Ctrl-PgUp or Shift-End you’d get it wrong. And when you’re in the zone, that’s a horrible, jarring experience – every time it happens it interrupts your flow, wrenches you back to reality and makes you want to throw the damn thing across the room. Imagine driving a car where the brake pedal is above the accelerator instead of alongside it – it was a truly unpleasant experience.

Fortunately, it didn’t take long for them to realise this one was a bit of a mistake. A year later in 1999, they came out with the Natural Keyboard Pro, and it was fantastic.

By ----PCStuff via Wikipedia, CC BY-SA 2.5, Link

All the keys were in the right places, and it included a two-port USB hub which was great for plugging in your mouse. It added a bunch of “multimedia” buttons (which I never really used) and a dedicated button for launching the Windows Calculator (which actually proved to be surprisingly useful.) I loved this keyboard dearly. You can guess what happened next… yep, I used it until it wore out, went shopping for a new one, and… yeah. No more Natural Keyboard Pro. Instead, we had this delightful triumph of form over function:

photo via Engadget

The Microsoft Natural Multimedia Keyboard, released in 2004. OK, it’s got the classic inverted-T cursor keys (yay, but - look at that! Not only are the navigation keys all wrong, but the Insert key isn’t even there; we’ve got a massive double-height Delete key instead. If memory serves, Insert was relegated to some sort of funky combo involving the PrtSc key. Oh, and this was also the keyboard where you had to keep F-Lock switched on all the time because the function keys were actually some sort of weird keyboard shortcuts that nobody ever used ever. You know. Like a dedicated key for “Send”, because Ctrl-Enter is just too complicated.

Again, it didn’t take long for them to come out with something better… and boy, did they ever get it right with the next one. The Microsoft Natural Ergonomic Keyboard 4000.

photo via

This was my main keyboard for most of the last decade. I loved this keyboard so much I actually stockpiled it – one at work, one at home, and a few spares standing by in case they wore out. And wear out they did, one by one, until late last year I decided it was time to replenish the stockpile… which is when my long-suffering colleagues half-jokingly asked if, maybe, I’d be prepared to try something quieter. See, the 4000 is lovely, but it’s noisy. The keys have plenty of travel, with a nice satisfying thump at the bottom of each keystroke, and the keyboard’s casing – which is big – makes a rather effective sounding-box. Until the bottom falls out of the London real estate market and we can justify private offices for our developers, FogCreek style, the open plan office is an unfortunate fact of life for most of us… and so, in the spirit of workplace harmony, I ordered a Microsoft Sculpt keyboard.

photo via Microsoft

And you know what? It’s pretty close to perfect. It’s comfortable. It’s quiet. It takes up about 60% of the desk space that the old Ergonomic 4000 did. The numeric keypad is actually separate, which I’m completely undecided about… when you actually want to type on it, it’s annoying not having it fixed in place, but being able to pick it up and use it like an old-school calculator is actually surprisingly useful. Except – yep – the navigation key layout is all screwed up. Again. I hit Insert by mistake all the time on this thing, and frequently land on the left cursor when I’m reaching for Ctrl.

But with the release of the Surface keyboard at the top of the post, it looks like, yet again, there’s a truly great keyboard hot on the heels of the not-so-great one. I’m just really curious as to why they keep bringing out models that use non-standard keyboard layouts.

photo via Microsoft

When it hits the market here in the UK, I’ll pick one up and let you know how I get on. Now, if they’d only release one that was completely black – with no key markings – then we’d really be onto something. I wonder if you can spray-paint it...