Tag: commands

How to: Use tagging in Git (Part VII)

How to: Use tagging in Git (Part VII)

Tagging is a great feature of Git and most other VCSs for that matter, that allows you to hmmm… tag (a warm round of applause for Captain Obvious) specific points in history as being important.

And this is the exact context in which Semantic Versioning starts to make more sense than ever. Following the wisdom within these two posts will at least make you look serious about software development, releasing new versions and fancy patches and stuff…

Listing Your Tags

Running the tag command with no options or arguments will list all the available tags in your repository:

git tag

But you can also list only the tags with a particular pattern. The Git source repo, for instance, contains more than 240 tags. If you’re only interested in looking at the 1.4.2 series, you can run this:

$ git tag -l 'v1.4.2.*'
v1.4.2.1
v1.4.2.2
v1.4.2.3
v1.4.2.4

Creating New Tags

We can have two different types of tags: lightweight and annotated. I’m not going to go on about the differences between those two, or why one of them is better than the other, they are both acting like pointers to a specific commit, but I prefer annotated tags as they can store additional information and be signed and verified with GNU Privacy Guard (GPG) – which you can probably read more about in the man page or the official docs.

To create an annotated tag, just use the -a option with the git tag command like this:

git tag -a v1.0.0 -m 'Version 1.0.0'

Tagging

The -m option specifies the tagging message which is stored within the tag object, but if you don’t specify it, Git will launch your editor so you can type it in.

Note to self: I’m planning on writing some script at some point that would help me automate the creation of change logs for major and minor versions, based on the commit messages between versions or todo list entries.

Also if, say you forgot to tag an important commit sometime earlier, you can still do it now by referencing its checksum:

git tag -a <tagname>. -m '<message>' <checksum>

Update: One more thing, in case you made a horrible typo on the tag you just created (like I just shamefully did), there’s something you can do that works pretty much like the --amend option for git commit:

git tag <tag-name> <tag-name> -f -m "<new-message>"

That will create a new tag with the same name by overwriting the original, or you could pop up your editor to type in more complex messages by running:

git tag <tag-name> <tag-name> -f -a

Viewing Tags

Viewing detailed information about individual tags, to be more precise, can be done using the git show command followed by the tag’s name:

git show v1.0.0

Again, this command has tons of useful options but you’re gonna try them all out on your own. I’m now giving you some more interesting combos that might come in handy:

git tag -l v1* -n999

That one will display the first maximum of 999 lines of all the tags starting with v1 – feel free to filter these as you like and display more or less lines of the tag message.

git log --oneline --decorate --reverse v1.0.0 v2.0.0

Use the one above to display a list of all the commits between major versions v1 and v2 in reverse order.

git log --oneline --decorate --graph --reverse --all

Or list the entire repository history in the same format as the above while also displaying branch graphs.

Sharing Tags

For some reason, git push doesn’t transfer tags too by default, so it needs to be done separately. You can either do it one tag at a time:

git push origin <tagname>

or by using the --tags option for all tags at once (it will only transfer tags that are not already on the remote anyway):

git push origin --tags

After this, any clone or pull operation will fetch all the tags as well so you can just go and take a long nice poop because:

  • you deserve it
  • your repo looks legit
  • according to semver, it now also has a meaning
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How to: Undo changes with Git (Part III)

How to: Undo changes with Git (Part III)

Sometimes, you f*ck up. I f*ck up, you f*ck up, everyone f*cks up at some point, we all do it, it’s natural. F*ck, some people actually even make a living out of it and sadly, it is often the same people we look up to or those who run the country. But f*ck it. This section is still all about Git and Git is the magical land where f*ckups are undoable.

what-has-been-seen-cannot-be-unseen

However, in most situations it is probably more preferable to just log the mistakes too and make new commits that fix them to reflect an accurate change history.

But no matter the weather, even in dire situations where there have been more commits in the meanwhile, on top of the ones we’re trying to undo, we have a few options:

git checkout

Even though git checkout can help restore peace and order in your working directory, we’ll have to talk about it later too when we reach branching, as it’s primary purpose is way greater. Here we can use it to replace files in the working area with the files stored in the repository (at the current HEAD pointer or any ref pointer really). But note that, when not using branches, it is good practice to include a double bare dash -- to avoid confusion and any unforeseen consequences:

To restore a file in the working directory with the file located at the current HEAD in the repository:

git checkout -- <file>

To restore a file with the file located in the repository at a specific commit pointer:

git checkout 24f6daf6f -- <file>

Looks like we’re going to need to talk about the checksums anyway… Git generates a checksum for each change set, using the SHA-1 hash algorithm, which helps maintaining data integrity. It is the checksum that can be used to refer to a specific commit.

Typically, a SHA1 hash value is rendered as a 40 digits long hexadecimal number, but because of how unique they all are, it is considered safe to address them by only their first few characters (8 characters for instance is way safe).

git revert

This command is used to revert an entire commit. Well, in actuality it creates a new commit which mirrors the targeted one (i.e. everything that was added gets deleted, everything that was deleted gets added, thus all changes undone).

git revert 24f6daf6f

So, using the above command creates the new commit and opens your editor so you can customize the commit message.

git reset

Most commonly, you could find yourself using the reset command to do one of the following two things:

  • Unstage files: say you’re trying to build up a nice commit, stating multiple files and then by accident, a file that’s not supposed to be there just slips in and your staging area is ruined…
git reset HEAD

There we go, that command had the sole purpose of unstaging that file.

  • Undo multiple commits: using the following commands will actually move the HEAD pointer to a previous commit. We have three useful options for three different types of resets, as follows:

The soft reset is the safest reset there is, as it doesn’t change the staging area or the working directory:

git reset --soft 24f6daf6f

The mixed reset is the default option, it changes the staging area but not the working one:

git reset --mixed 24f6daf6f

The hard reset can be destructive as it changes files in all three areas – USE WITH CAUTION.

git reset --hard 24f6daf6f

Thing is, once the HEAD pointer moves back in time, all the other commits after it might seem lost, but they’re not – you can run the same command again, referencing any future commit you can think of (you can first output a git log to a plain text file to still have access to those checksums).


By now I assume you’re old enough to know that not every project is made of candy and each one of them is totally worth tracking and just as important as the next one. There will always be such things as small OS-specific temp files, cache files, logs, dumps and stuff that constantly changes just enough to make git flip out on every commit you make. In the next post, we’ll have a serious grown-up talk on How to: Ignore files in Git (Part IV).

 

Getting started with Git (Part II)

Getting started with Git (Part II)

After just a little over a week’s time from the first part of this series – Getting started with Git (Part I), I’ve managed to put together a basic, yet hopefully comprehensive list of git commands that should get you right on track with your workflow. Before anything, you must understand that initially, this post was over 30 printable pages long, which made me seriously doubt my mental capacity and then split it into multiple posts, one for each major section of it.

THE BASICS

Now, just to make sure we’re on the same page, know that Git doesn’t quite exactly track your files, but rather the changes you make to them. While this might seem useless in the event of a filesystem catastrophe (i.e. your files get lost / deleted / abducted by aliens and / or Pedobear), you best believe that it is more than enough to restore everything back to its previous state, provided that your project directory is still a git repository – which you can easily tell by the presence of a hidden .git folder in the root of your project.

Furthermore, with Git, you can actually restore the project to any state at any point in its development history, for which there is a commit entry. And even in case your whole directory is gone, you can still hope someone else has a copy of your repository and / or you can just clone the entire project from a remote… (you did use one, right?) Great, let’s get to it – this section will get you started with some basic commands for managing your git repository and making changes to it.

git help

The first command you might want to take a look at before anything if you’re just starting out, is git help. On its own, without any arguments, it will give you some general usage tips and a list of the most commonly used git commands, which is far less intimidating than the initial length of this post.

But the true power of this command lies in its ability to be used with other git commands to display their specific help page. Go ahead, give it a try for the next command we’re going to talk about:

git help clone

git clone

Sharp little young grasshoppa’ you are, aren’t you? You already know that git clone does wonders for your sheep then… Well, another thing it does is clone a repository into a newly created directory, creates remote-tracking branches for each branch in the cloned repository and checks out an initial branch that is forked from the cloned repository’s currently active branch.

Sheep Cloning

You can actually clone from local repositories too, but this command is more commonly used when working with remotes. Just as in the case with most of the commands described in these posts, this one has a bunch of interesting options that are thoroughly described in the man pages, which you should check out whenever in doubt, or ask questions in the comments section below. Up to some level, I’m somewhat of a guru and might even find myself posting questions and answering them later – which might be sad and funny at the same time, but all in all normal.

There are multiple variations on Git URLs and they can all be used with this command. Some of the most common forms would be:

  • ssh://[user@]host.xz[:port]/path/to/repo.git
  • git://host.xz[:port]/path/to/repo.git
  • http[s]://host.xz[:port]/path/to/repo.git

I’ve already posted a quick guide on how to make a git server that gives you those ssh:// URLs, and there’s another one on the way for a more elegant and secure solution that gives you the git:// URLs which are simply just prettier.

Then, a regular clone command would look something like:

git clone git://git.server.net/git/repo.git

That command will create a repo directory in your CWD, but you can override its default name by adding it as an extra argument:

git clone git://git.server.net/git/repo.git CustomName

git status

So basically, git status displays paths that have differences between the… wait. Did I tell you about the 3 Tree Architecture? Yeah, well Git uses it, as opposed to most other version control systems that are stuck at 2 Tree. Simply put, that only means Git consists of 3 areas or places to store things. Oh, f*ck it – too much talk – here’s a picture:

Git's 3 Tree Architecture

So, as I was saying, git status displays paths that:

  • have differences between the Staging Area and the Repository (can be committed)
  • have differences between the Working Copy and the Staging Area (can be added, then committed)
  • are simply not being tracked by Git and can be added (and are not ignored, more on that later…)

This is already too long of a post, so I might as well talk a little bit about some of these terms:

Working copy would be your actual working directory on your local machine where you make your changes.

Staging Area is that magical place where pending changes (files that were added using git add) wait to be committed – think of it as an intermediate step that allows you to build custom commits, organize your changes into commit batches.

Repository is the final destination of your changes, the place that stores your commits and their specific messages.


Committing is the process of moving the changes from the Staging Area to the Repository.

Adding would be the process of telling Git to start tracking a file or group of files and adding it to the Staging Area.

At this point, I sure as hell hope that all this typing will somehow offload the task of having to explain every minor little thing that will come into context… It’s all nice and interesting but not of utmost importance for someone who’s only going to be typing these commands and move on before it all becomes routine.

On a second bipolar thought, I’m glad I know about these things and if I ever stop knowing, at least I could get a good idea on what to want to know. My logic is impervious… and this, having been a long day is no good excuse. This post will either amuse me later on when I’ll review it or cause some serious self-pity as I go all emo.

git commit

At long last… wait. Did I tell you about the SHA checksums? Kidding… for now. But really, if you’re afraid of commitment, this is where you should stop reading ’cause we about to commit. Git it? We’ve already covered what the commit does, moving stuff from the Staging Area to the Repo, you only need to know that any commit needs to have a message associated with it (I keep hearing there will be an awesome post on writing good commit messages soon):

git commit -m "Your significant and concise commit message"

Note: You cannot commit files that Git is not currently tracking.

To start tracking files, you need to git add them:

git add /path/to/file.ext

You can add multiple files simultaneously and even use wildcards, or you can just simply add all the files in your project:

git add .

Another useful thing to know would be the shorthand for adding all files and committing at the same time:

git commit -am "Yet another fascinating commit message"

Yeah, and then there’s the --amend option – you can use it to squeeze in another commit within the last commit in case of a minor f*ckup (i.e. you forgot to add a file or change a title somewhere):

git commit --amend

That command will open the core editor allowing you to change the commit message of the most recent commit. Additionally you can set the commit message directly from the command line:

git commit --amend -m "The new and improved commit message"

Yes, the amend option comes in handy even when there aren’t really any changes and you only want to just maybe correct a typo in the previous commit message or something.

git log

The command that lets you view all of the commits with their messages and other associated data – a command with many many options and a man page that’s really really worth going through. Soon as you start loving it, you’ll realize how important good commit messages are… Here are just a few tips:

git log                   # To view all the commits ever made
git log -n                # To limit the number of commits
git log --oneline         # Compact view, for large projects
git log --graph           # To visualize branch merges
git log --author="John"   # View only commits made by John

Also, you can filter commits by date:

git log --since=2014-09-03       # Commits since 2014-09-03
git log --until="two weeks ago"  # Commits until 2 weeks ago

Oh, it gets better – with regular expression filters:

git log --grep="[bugfix]"        # Look for bug fixes
git log --grep="[css]"		 # Look for CSS

Yes, the first line of commit messages could include tags, so that you can later on use git log to filter them…

git diff

Yeah… I’m not going in depth with this one – it’s not really much to it, but for my diff-ing needs I usually rely on third party apps / plugins since I’m not even that much of a fan of Unix’s diff command either.

The git diff is quite similar to it but works with different types of arguments like git trees or tree-ishes, blob objects, actual files on disk and all kind of combinations of all of the above. The official man page does a way better job describing it all than I ever even would be willing to.

But I don’t wanna be the bad guy here, so here are a couple of tips:

git diff             # Working vs. Staging for all files
git diff <file>      # Working vs. Staging for <file>
git diff --staged    # Staging vs. Repository

The command can also be used to compare two or more branches:

git diff <branch-1>..<branch-n>

Note: The --color-words option can be used to suppress duplicate lines in the output and highlight only the changed parts.

git rm / git mv

There’s nothing really special about these two except the fact that they handle file moving, renaming or deleting inside a git repository the right way.

Their Unix-specific counterpart commands have their ways of affecting Git’s staging area by messing up the tracked and untracked files (that’s a pretty long and boring story) but I don’t mind a few extra steps cleaning after them so, yeah…


Committing stuff regularly is generally a good thing, think of it like the save / autosave feature in well, really any respectable game out there. Besides that, you have full control over when and what to save, and even then, sometimes things can go horribly wrong. In the next post we’ll go over a bunch of ways that we can Undo changes in Git (Part III).