EVERY SINGLE TIME I unshelve a changeset with add/rename/move/remove changes or
have pending changes with such changes, I have to manually merge the parent project file which receives a lot of activity (the majority of the codebase is nested under the one project so its project file's version changes very frequently).
This is a multiple-times-per day frustration and it seems that TFS should be able to do this for me since the changes are simple (e.g. remove the line for the deleted file in latest version and add the line for the new file in local version). I conclude this because it behaves intelligently in this way for code files to automerge versions.
So why does automerge behave differently with project files than with code files?
For example, developer A creates a changeset adding a file to the project and shelves it for review. Then another developer B checks-in changes to the project that also adds a file (unrelated), so when I go to unshelve developer A's changes I have to resolve conflicts on the project file.
Also, if a group of files are moved/renamed/added and I want to unshelve with only a single affecting change, it is much easier to just take the server version of the project file and manually reapply the single change (e.g. add existing file) instead of merging a dozen spread out changes across thousands of lines. (And god forbid you have a rename change and took server version of the project file, because then you need to manually edit it with a text editor to rename otherwise you'll get a sequence of errors due to the renamed file already existing on disk when trying to rename from solution explorer).
Update: I'm escalating this, because now it's screwing us over.
Using VS2014 and our codebase mostly lives under one giant database project (*.sqlproj).
Most likely, different files get added on the same line in the file since in most cases, project files are auto-generated, unlike regular code, it is hard to tell in which line VS would insert a new file item when someone adds it on the front end. If 2 people add new items to the project at the same time, it is very likely that you will get 2 versions of the project file with these new items written on the same line, which will cause the conflict. Sometimes, (e.g. if you add reference), it's more than one line per item, which makes merging even worse.
I would suggest that each developer that makes changes to the project file, checks it out with the lock (exclusively), so there will be one change at a time. Also, make sure other developers get latest before making their change (there is a setting in Visual Studio under Tools > Options > Source Control > Visual Studio Team Foundation Server). This will make auto-merge work.
If I have files checked out and run an update later, I'll usually come across a conflict which gives me a few options to resolve. If I pick the 'keep local version' option, do my changes replace the server's version without updating the history?
Is there a reason why you would want an option to alter your source code so secretly?
Nothing changes until you check in the file and you will always have the history and annotations.
Typically unless you have a good reason not to you will want to merge conflicted non-binary files and use common sense when choosing whether to take an updated binary file or not. If it is a non-binary merge pretty much the only time you would keep local is if you specifically knew you didn't want the latest changes since you check the file out to make it in to your copy.
When merging, everything happens on your PC - nothing is checked in to the server.
You have three options:
Keep the server version. This is very much like an "undo checkout" and it overwrites your local copy with the server's version of the file so your local changes are lost.
Keep the local version. This ignores what is on the server and keeps the version on your PC, so your local changes are preserved.
Merge. This allows you to use a diff/merge process to pick and choose text lines from your source file and the server's source file, which allows you (a) to see exactly what has changed in both versions, and (b) decide what the final result should be (all the server's changes, all of your changes, or (usually) some hybrid mixture of both of them.
After you merge, if you have used either of the options that will alter your local copy, you really ought to rebuild your project and check that the changes introduced have not broken your code. You can then continue your work and check in when you are confident that everything is working.
The best approach to use with source control is to aim to make small self-contained modifications that you can check-in frequently (e.g. once or twice a day). Similarly (after checking that the net code is safe to take, e.g. with continuous integration), get the latest code fairly often (after every check-in, and preferably no less than once a day). This team strategy minimises the chance of your changes clashing with those of another developer and a merge being required. In the cases where a clash does occur, it is generally quick and easy to resolve because you are taking small bites of the code frequently, rather than working "offline" for weeks and waiting for thousands of changes to build up on the server. Merges are often complicated and difficult, so choosing strategies that minimise the need to merge can be a very beneficial approach.
When I merge files from one branch to another and then go to check in files into the target branch, there are MANY files checked out, just the ones that changed. For example, Main and Critical branches were the same and we made changes to only 2 or 3 files on the Critical Fix branch. I then merged Critical ==> Main, and when I went to check in changes to the Main branch I noticed that there were numerous files checked out, not just the 2 or 3 that were actually changed in the Critical Fix branch. Moreover, when I compare a file from the Main branch to one on the server, I am told that the files are identical. If the files are identical, why are they checked out? Any help would be appreciated, or even a link that explains how TFS 2010 does merges.
The default Source Control Merging tools in Visual Source Safe and then TFS have always been rather poor - they are often confused by the simplest changes, often detect identical files as being "changed", and the auto-merge facility frequenty fails (includes the wrong changes). I quickly learned distrust for these merge tools (in about 1995) and have not seen any evidence in any of the new releases since then that the core merge algorithms have been improved at all.
The good news is that you can replace the client-side merging tools with third party ones (I use one that works so well that I actually trust its auto-merge option. I once spent 2 days trying (and failing) to do a complex merge with the TFS tools and in the end bought this 3rd party tool and re-did the entire merge successfully in 15 minutes!)
The bad news is that the first step of branch merging just uses the TFS merge code, and so it gets confused a lot, resulting in the symptoms you've described. This is frustrating in such a key feature of such an expensive application as it wastes a lot of programmer time on every merge to fix imaginary "conflicts" - on the plus side, with the help of 3rd party tools it is usually very easy to reliably resolve these merge issues.
I have had the same problem. I created a branch of our DEV branch and made changes to a few files. I checked in my changes and merged the latest changes to DEV into my branch. After the merge all 30,000+ files in my branch were marked as changed. Just like cju, I found that a comparison of most of the files showed that no changes had been made.
I decided to undo all changes and try again. When I right-clicked on the solution and selected Undo, I got a message that one file had changes, was I sure I wanted to undo that file? I clicked "No to All" and when the undo operation was complete, only the files that had been changed during my merge from DEV were still checked out. This was exactly what I wanted so I checked those changes into my branch and continued working.
I hope others can correct their situation as easily as I was able to.
One thing I noticed is that when one file is changed in different branches resulting in exactly the same content, then merging marks it as a conflict since the file is changed in both places. Of course a difference view of the file notices that there are no changes and therefore an auto merge solves this automatically for you.
I've used TFS for about 18 months now and I'm really not excited about it. It seems like the worst of the current versions of SCMs on the market.
I think this thread will help people decide if TFS is for them vs. other source control systems. While TFS does a lot more than that, I think that source control is so critical to software development that any system (or combination thereof) that you pick needs to consider source control first.
What are the good things about TFS vs. other source controls -- what does it do well that no one else does?
What are the things that TFS is bad at that everyone else seems to do just fine?
Pros
Fundamentally it's a sound system. Robust and reliable.
Integrated with work items, reporting, etc.
The power tools are really good.
[edit] It is improving, and has taken good jumps forwards with 2010, 2012, 2013
TFS is highly accessible for custom tools. There's a rich API that makes it so easy to write dashboards and other tools to get at the data in TFS. And as all the data is stored in SQL, you can browse it and query it directly if need be. I've worked with many different SCMs over the years and have never found one that is so open and accessible - everything (user stories, tasks, bugs, issues, test plans, iterations, source code control & branches, builds, unit testing, continuous integration) is just there at your fingertips. This is an awesome feature of TFS. A lot of the UI failings of TFS have been addressed in a few afternoons writing tools and a dashboard for my team to use. And let's face it, if you write your own, it does exactly what you need.
Cons
There is one area where the robustness fails miserably: If you apply several changes to a file (add, rename, edit) in "one go" it gets horribly confused. If you don't check in these actions separately, both TFS2005 and TFS2008 crash when you go to merge those changes across branches. In 2010 onwards it no longer crashes, but it often doesn't correctly check in the changes, so you have to go in and clean up a mess of missing and incorrectly named files.
There is no standalone source control browser. It's integrated into VS, which is really annoying when you want to just work on source control items without needing to run up another copy of VS. Of course, you can give your artist a Team Explorer, but let's ask ourselves if an artist who only ever wants to view the files, check out, check in, and GLV really needs a fully blown complicated VSTS instance running to achieve it? In addition, the integration is so poor that you can't realistically use TFS from the Solution explorer (it simply lies about what you have checked out, and is so unreliable when you apply actions from that window that you soon learn to open the source control window and work in there, which defeats the point of it being integrated in the first place) [edit: The file explorer extension is excellent - close to a standalone browser - and is simple and easy to use. The main drawback of it is lack of proper integration with file commands - to rename or delete files you must remember to use the TFS submenu, or you will rename/delete locally and this screws up source control completely as TFS knows nothing of the changes you have made. This unfortunately means that only 'advanced' TFS users can be trusted to use it. So, essentially, it's still a case of "no stand alone browser" for most users]
The user interface sucks (but is improving, at least on the web-access side). Sure, it works, but there is so much that could be done to make it efficient, pleasant, and more foolproof to use. e.g. [prior to 2012] When you click "check in" it ticks all remaining un-checked-in items so that if you accidentally click Check in again in future, it checks in a load of stuff you didn't want to. And after this, it would be so easy to supply an "undo last checkin" option to quickly roll it back - but there isn't one. [Edit: The UI is improved, but these specific problems are still present in VS2010, although it does now have a check-in confirmation dialog that reduces the risk of accidental checkins][edit: in 2012 it's much better, but they've gone mad and rolled all the separate TFS dialogs into a single window, which was a serious step backwards. The pending changes window doesn't work nearly as well as in 2010 - it is harder to find things, it takes more clicks to achieve the same things, and if you check in a file from anywhere all the currently 'included' files get chucked into 'excluded' so if you have several things on the go they all get mixed together]
Workspaces. In most cases, every team member has to have essentially the same workspace mapping, slaved off a local root folder. We need 7 mappings defined, which takes about 5 minutes to set up. There is no way to push the workspace definition from the server. There is no [edit]easy[/edit] way to duplicate a workspace so you can use an existing one (or another users one) as a starting point. No, you have to manually re-enter all the bindings over and over and over and over. If you change your active workspace in the source control explorer, it doesn't get synced to your pending changes window, so you spend 15 minutes wondering why the file you merged from your other branch just isn't listed. [edit: This is getting better with 2010/2012, as you can see workspaces on other PCs and copy and paste them more easily, but it's still a pretty clumsy UI]
It has changesets, but you can't bundle items into separate changesets in your pending checkins list as you can in Perforce, you can only associate them with a changeset by actually checking them in. You can really only work on one changeset at a time, or you have to separate the files out manually in your pending list as you go to check in. [still very poor in 2012]
The merge tools are terrible. As in: they simply don't work, and unnecessarily introduce bugs into your code if you rely on the automatic merge. These tools are just as bad as they were when I first used SourceSafe in 1994. So the first thing you have to do after buying a very costly VSTS licence is replace the merge tools with something that actually works. And that means that every time you get a merge conflict, you must select each file. Choose to resolve the conflict and ok. Choose to use your 3rd party merge tool and ok. Then merge. Then save. Then choose to accept your merged changes. (You should be able to choose "automatic merge" and have it simply use the third party merge tool that actually works without hitting you with a barrage of pointless and annoying dialogs that always default to the wrong option) [Edit: InVS2010 the merge tools are still awful. But the front-end UI is much improved (merging a conflict now takes a single click rather than 4 or 5 clicks - a massive improvement when you have to merge many files][In 2012 there have been further improvements, but they are still 'ok' rather than good]
It doesn't sync between running instances of VS. So if you check in a file in one VS, another one will still list that file in your pending checkins. (it's clearly easy to sync it because any changes made by the power tools windows-explorer extension are reflected in VS instantly). [Edit: In 2012 they have fixed this problem. Now every time you switch to the pending changes view it spends 15 seconds refreshing (in 2010 it cached it and showed it instantly but it was occasionally out of date)]
Branching is the standard way of working these days. So you'd expect the branch/merge tools to make this quick and easy. But no. [edit: Big improvements were made in 2010 and 2012, but merging is terribly supported - it is really labour intensive. Just little things like only being able to merge a contiguous set of changes, so if you want to merge 5 changes that are not contiguous you have to do them one by one, but each time you open the dialog it starts from scratch instead of remembering where you were, what you last merged, the list of availablke changesets, etc. You should be able to select any changesets you want and it should automate the rest]
If you GLV (get latest version of) a solution, and some of the projects in it have been changed, VS repeatedly asks if you wish to reload each changed project. It is about 10x faster to close your solution, then GLV, then open the solution again than to GLV with it open. If I'm GLV'ing then of course I want to reload the projects! When I buy my food at the supermarket they don't ask me for every item "do you wish to take this item home with you?". [Edit: Still broken in VS2010][Fixed in 2012. Hurrah!]
[edit] If two team members add a new project to a solution, then when the second person goes to check in, they must (obviously) resolve a merge conflict. However, TFS treats the .sln as a text file, and corrupts it (it adds the two project entries but the project count is effectively only incremented once). It would be so easy to fix the sln format to make the files mergeable.
[edit] I don't do any source control operations from within the Solution Explorer window, as it has been rather unreliable ever since "integration" first came along. Even in 2008 it usually has random "checked out" icons on files that are not checked out, and recursive operations sometimes do weird things. Almost every source control 'glitch' we have is a result of someone starting an operation from the Solution Explorer. Luckily, I prefer to work in a Source Control window anyway.[2012: Sorry, can't tell you if this is fixed, as I haven't used this feature since 2008]
[edit] Where to start with the Source Control Bindings window? VS could say "Your Source Control settings have been corrupted again for no obvious reason. I never could get the hang of Thursdays. Shall I fix this for you? [YES]", but instead, it shows a complicated, confusing dialog full of information that makes no sense to anybody, resulting in a UI so scary that it makes junior programmers soil themselves. The trick is to ignore the whole window, hide behind your desk and click the "fix it" button, and it fixes it.
[edit - added 12/2010] When you Get source code, especially when resolving merge conflicts, other windows are often brought to the front (either the Solution Explorer jumps in front of my Pending Changes view, which I have docked in the same tabbed area, or the Source Control window vanishes behind another document window. This is really annoying when you have another file to merge or another folder to Get, as you have to keep "finding" the Source Control/Pending Changes windows. Getting code should not constantly reorder my document/tool windows.[2012: Still broken]
[edit - added 1/2014] With TFS 2012/2013, there is a choice of Server or Local workspaces. Server is the name for the old system where you must be online with the server to check files out. Local is the new default and makes a copy of the entire source repository on your computer, allowing you to make edits to any files without needing to check them out first. TFS then diffs your files against its local copy to work out what you changed. This sounds good, and for many people it probably is good, but it has some serious drawbacks that you should be aware of:
As you no longer check out files, they do not get locked when you edit them, and thus several people can edit any given file simultaneously, requiring a merge operation when they check in. This is fine for text-based source code files, but results in difficult situations or lost work when the files are unmergeable. Unmergeable or non-automatically mergeable files include Solution, Project, Resource (resx), XAML and any other XML files - so this causes a lot of problems in a development environment. If (like us) you also want to store Word and Excel documents and binary files under source control, local workspaces are positively dangerous. We have lost several days of work because someone unwittingly used a local workspace and then it was not practicable to merge their changes. You can reconfigure the TFS server to make Server workspaces the default to defend against this.
With Local workspaces you have to keep two copies of everything on your computer. When we upgraded TFS we suddenly found everyone lost 25GB of disk space, and it took several weeks to work out where the disk space had gone! This was a major problem for us because we all use SSDs and it is only now (2014) that SSDs are getting large/cheap enough that we can afford to be so inefficient with our disk space.
In the few weeks that we used local workspaces we had several incidents where TFS corrupted files or lost changes, presumably due to bugs in the implementation. Quite simply, we cannot accept anything less than 100% reliability for our source control system.
TFS is getting much easier to manage; these days if you don't want to customise anything too much you can set up a server in a very short time (hours) and setting up continuous integration builds and backups etc is extremely easy. On the flip side, while I found it very easy to set up backups of a TFS database, restoring that database and getting up and running after our server bricked itself was another matter - it took 4 days to work through all the unnecessary blocking problems (e.g. you have to restore the backup form a network drive, the data can't be local. When I tried to restore the image to the rebuilt server, TFS kept telling me there were no databases that could be restored. When I got past that, TFS wouldn't use the databases because they didn't match the host server (because that server was gone, the OS had been reinstalled). It took a lot of searching and fettling to get the backup to restore. Restoring should "just work"!
As you can see, most of the above are just trivial UI gripes. There is such a lot that could be improved about the UI. But the actual underlying product is good. I prefer TFS to pretty much every other SCM I've used over the last 28 years.
I wouldn't even mind the poor UI so much, except that it is one of the core UIs developers have to use on an hour-by hour basis, and they have to pay such a lot to get it. If the subscription money from a single developer was invested on improving the UI it would make a massive difference to the usability of TFS! It's painful to think that TFS is merely good or ok when it could so easily be excellent with a bit of nice UI.
Hates
Doesn't track changes to files unless you've checked them out, so if you edit a file in Notepad++ TFS is unaware that anything changed.
It's very easy for someone to check out a fille and lock it so that nobody else can make changes. TFS shouldn't drop this ability, but it certainly should make it much harder to do than it is currently.
The methods to undo a commit or two is very unclear, so much so that I'm never quite sure if it worked or not.
The way that TFS makes files read only unless you check them out is obnoxious, though it does help me remember to check files out before I save the edits I've made.
Loves
I suppose built-in integration with visual studio is nice, if you like that kind of thing (I don't)
I am a member of the Team Foundation Server team at Microsoft. There are a lot of very valid issues raised here. Some of them are addressed in the 2010 release. Others remain as issues, but we do recognize them and are working to improve the developer experience with the next release. Discussions like this are great for helping us make sure we're solving the right problems.
Here is some info on issues that are at least partially addressed today in the 2010 version:
Stand alone client
For non-developer customers that want to use the product outside of VS, they can use the Windows Shell extension powertool.
If you have users (developers or not) that need to access TFS from non-Window machines, they can use Team Explorer Everywhere. This is supported on platforms including Mac & Linux.
Copy workspace
There are two ways to copy a workspace today. The 1st is by using the workspace template command at the cmd line. Ex.
Tf /workspace /new /template[workspace name/owner to copy from]
Alternatively, you can open a workspace in the UI, select all of the mappings, copy them, & then paste them into a file/email. Someone else can than paste those same mappings into their workspace.
It would definetly be great if you could simply specify a default workspace that clients automatically pick up, but we don't have this today.
Merging robustness
The scenario described where you do an add, rename, add & then have problems when you merge has been addressed in TFS 2010.
Branch/Merge as a 1st class experience
In TFS 2010, branches are now 1st class objects in TFS. You can visualize your branches & even track changes as they move through the branch. Branching is also now a fast server based operation.
Get Latest Version of multiple projects
You can do this today by choosing the TFS instance node in source control explorer & then selecting get latest. This is the equivalent of the root folder ($).
File locking
By default TFS never locks files when users checks them out. This is the way we use TFS at Microsoft & how we see the majority of our customers using TFS. It is possible to enable users to explicitly lock files. Some customers find this desirable, but it is not the default path experience.
Con: Checkout model. Many applications do not deal well with files that are marked as read-only then change to writable (Word 2007, Notepad). So you open a file, edit the file, try to save then you're told that you can't save because it's read-only. Great, now you have to Save As..., delete the original and renamed the new one to the old name. If there's an upside to having local files be read-only I don't see it. I really prefer Subversion's approach to this.
The one upside to making files read-only is that it reminds you to check them out. However that's really just a symptom of the check-out model.
I think that TFS is the single best ALM product on the market today. Looking at it from only a source control platform is slanted. I have used many products in my career to date: VSS, SVN, Git, StarTeam, CC/Harvest, and ClearCase - apart from TFS. Personally, I cringe at the thought of going back to anything other than TFS.
TFS is an extremely powerful platform. My biggest problem with it is often related to people not knowing how to use it or using it incorrectly. It is not meant to be an application that "just works". Sure, you can use it for basic source control without learning much about it - but if that is all you use it for, then you really are better off using one of the less robust tools out there. In reality, what TFS does not give you is the way to interpret features how you want to. It is specifically built from the ground up to support process and not just be a repository.
Con: Timestamps. There's no way to set TFS to use the remote last-modified timestamp as the local last-modified timestamp. The local file's timestamp only tells me when I got the file. If I get a file that's 2 years old, there's no way to know that based on the local timestamp.
Other source controls that I have used have this ability.
Cons:
workspace version: You can't identify the version of a workspace without doing a recursive search.
terrible offline experience. attrib -r + tfpt online shouldn't be the way to work offline. Give me something like git that allows me to track status, undo and make changes. I'm even fine if it only stores the difference between the workspace version and current.
Merging robustness: a changed file on the server + a local edit on different lines is not a conflict. a writeable file should not be an automatic conflict. The automerge button should NOT exist, because it should never be a scenario.
Workspaces: the idea of being able to rearrange the source structure is just odd, and causes issues. the requirement of having both branches mapped in order to merge is odd. The requirement of having to do an operation multiple times, because my workspace mapping doesn't have a true root folder is wrong.
Full reliance on remote server: There are some nice things about having all these things stored on the server, but really, you could store information locally and then upload it when needed. Keep pending changes, workspace mappings, basic undo history locally, etc.
Pros
Shelvesets: I love these, and wish support for them was brought to the local disk as well (think git stash)
Source control view in VS: It's pretty cool to be able to view the entire repository without downloading it. There are some usability issues, but the overall idea is cool.
Workspaces: yep, both places. While re-arranging a repo is odd, the ability to only download what you need is pretty awesome. I often wish I could choose a root folder and then check box the paths I need, but oh well.
Dislikes:
Using the history to figure out what has been done is cumbersome to say the least. You have to click on every single history entry to see what files were changed, and then you need to go through a context menu to get a diff.
Working while disconnected from the network is a big no-no. Ever heard of working on an airplane?
No Windows Explorer integration for when you work with files outside of VS (think TortoiseSVN).
Process methodologists (configuration managers) love to not allow shared check-outs. This is absolutely horrible for example for config files that you need to modify for testing.
SC gets confused with complex move/delete operations.
SC does not recognize when a checked out file has not changed. For example, service reference updates check out all related files and often regenerate the exact same content. These files should implicitly be removed from check-ins because they just add noise when you look at your changeset later.
Likes:
Shelving.
Anybody guessed which is my favorite SCM system? SVN + TortoiseSVN + VisualSVN :-)
Search functionality is not implemented in TFS 2010 ?
VSS we have search in file; TFS 2008 we have search file ...
Con: If you want to move multiple files to a subfolder of the existing location, you have to do that one at a time. Wow, that's horrible.
The lack of rollback has been my biggest pain point.
The lack of true rollback support and the inability to rename a TFS Project are my two main pet peeves with TFS. Other than that, I've been very happy with it for 2-3 years.
The fact that certain applications do not support in-edit changes from read-only to writable (forcing you to reopen the file in question) is annoying but is really a problem with those specific applications. The fact that a file is read-only while not checked out has certain uses, one of which being that it reminds you to check out the file. It does occasionally, however, lead to confusion when trying to get specific revisions of files. Writable files are not re-downloaded unless you enable a flag, because they're considered local edits.
I am trying to come up with best practices regarding use of TFS source control. Right now, anytime we do a build, we label the files that are checked into the TFS with the version number. Is this approach better or worse than simply checking the files in and having the version number in the comments?
Can you then use the changeset to go back if necessary or the labels are still more versatile?
Thanks!
They have two different purposes, ChangeSets are when the files have actually changed and you wish to keep a permanent record of that change. Labels mark a certain version of the files so that you can easily go back to that point. Unless your build actually changes files under source control and you wish to record these changes. You should be labeling.
Also, labeling is much less resource intensive. And you can have multiple labels on the same version of a file.
You should label the versions of source files that make up your build. If you're using TeamBuild, it does that for you automatically. It combines the name of your build definition, date, and the build number. So you don't need to do anything.
Your other option is not very conventional and requires a lot of unnecessary work. If I understand it correctly, you would check out your source files during the build process and then check them back in with a version number specified in the check-in comments. This is as Alex mentioned very resource intensive in terms of your build process and also your source control repository. Moreover, how would you get the source files for a particular version if the version information is embedded in the comments? It will be very hard and you would have to sit down and write your own application that uses TFS source control api to download the source files to a workspace by searching for the version number in the check-in comments. This creates unnecessary complexity and headaches.
If you use labels instead, you can do a get by label in VS IDE to download the source files that make up that label. You can even tell TeamBuild to use a label instead of downloading the latest source files during build automation. That way you can build previous versions of your application easily. With labels, you can also apply later changesets to an existing label if there were code changes by simply getting that label and then getting specific changesets and then doing a quick label or creating a brand new label.
Labeling is very powerful, convenient to use, and is a part of TFS. Rather than coming up with your custom solution that requires a lot of effort to make it work and maintain, just try to use what's already available.
Right now, anytime we do a build, we label the files that are checked into the TFS with the version number
You don't need to do this. TFS can refer to a state of the codebase in numerous ways, of which labels are indeed one - but so are builds and even changesets. You can see the available ways to reconstruct a particular point in time by doing a Get Specific Version... and examining the options in the Type dropdown:
Changeset
Date
Label
Latest Version
Workspace Version
Changeset allows you to get just after any changeset; Date is obvious; Label is too, except that builds automatically* create labels (choose Label from this dropdown then have a look in the Find Label dialog).
*I think it's automatic! Unless it's something we've set up specially where I am at the moment...
StackOverflow won't let me comment on the answers above, so I'm writing this as a new "answer". I want to clarify some of the misconceptions listed above.
First, using TFVC Labels is MORE resource intensive than using changesets. A lot more. Commands such as Branch, Merge, and Get by Label is slower. For enterprise servers with huge databases you do not want to be using labels.
Second, Builds don't automatically create labels, although the default build steps include a step to create a label.
Third, as others already mentioned, labels can be moved or deleted, so they are much less dependable than changesets which are immutable.
Overall I recommend you NOT use labels. The simplest alternative is to just remember the changeset number for your builds. Or if you want to isolate different release versions, you should create release branches.
Labels are OK for small systems, but are not good for large enterprises.