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Git Essential Training
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Writing commit messages


From:

Git Essential Training

with Kevin Skoglund

Video: Writing commit messages

In this movie I want us to talk about writing commit messages and the best practices for doing that. Now in the last movie we did our first commit, and we gave it a really simple single-line commit message that was just initial commit, pretty bland and boring and even worse, it doesn't really describe what we were doing. What you really want to do is have a commit message that describes the changes that you're making in that commit set, so added file to project, that would be more descriptive saying that we added this first file. That you added the JavaScript to something, that you were fixing a bug.
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  1. 2m 46s
    1. Introduction
      1m 7s
    2. How to use the exercise files
      1m 39s
  2. 20m 24s
    1. Understanding version control
      4m 48s
    2. The history of Git
      7m 58s
    3. About distributed version control
      5m 4s
    4. Who should use Git?
      2m 34s
  3. 26m 12s
    1. Installing Git on a Mac
      3m 44s
    2. Installing Git on Windows
      5m 37s
    3. Installing Git on Linux
      1m 30s
    4. Configuring Git
      7m 29s
    5. Exploring Git auto-completion
      5m 35s
    6. Using Git help
      2m 17s
  4. 15m 49s
    1. Initializing a repository
      1m 58s
    2. Understanding where Git files are stored
      2m 34s
    3. Performing your first commit
      2m 4s
    4. Writing commit messages
      5m 22s
    5. Viewing the commit log
      3m 51s
  5. 17m 44s
    1. Exploring the three-trees architecture
      3m 57s
    2. The Git workflow
      3m 15s
    3. Using hash values (SHA-1)
      4m 7s
    4. Working with the HEAD pointer
      6m 25s
  6. 25m 52s
    1. Adding files
      5m 59s
    2. Editing files
      3m 56s
    3. Viewing changes with diff
      3m 35s
    4. Viewing only staged changes
      2m 28s
    5. Deleting files
      5m 29s
    6. Moving and renaming files
      4m 25s
  7. 19m 18s
    1. Introducing the Explore California web site
      2m 2s
    2. Initializing Git
      3m 48s
    3. Editing the support phone number
      6m 20s
    4. Editing the backpack file name and links
      7m 8s
  8. 38m 45s
    1. Undoing working directory changes
      3m 49s
    2. Unstaging files
      2m 37s
    3. Amending commits
      4m 50s
    4. Retrieving old versions
      4m 7s
    5. Reverting a commit
      3m 12s
    6. Using reset to undo commits
      3m 44s
    7. Demonstrating a soft reset
      4m 8s
    8. Demonstrating a mixed reset
      4m 7s
    9. Demonstrating a hard reset
      5m 8s
    10. Removing untracked files
      3m 3s
  9. 27m 22s
    1. Using .gitignore files
      8m 23s
    2. Understanding what to ignore
      4m 47s
    3. Ignoring files globally
      4m 49s
    4. Ignoring tracked files
      5m 26s
    5. Tracking empty directories
      3m 57s
  10. 26m 51s
    1. Referencing commits
      4m 52s
    2. Exploring tree listings
      3m 46s
    3. Getting more from the commit log
      7m 38s
    4. Viewing commits
      4m 4s
    5. Comparing commits
      6m 31s
  11. 39m 35s
    1. Branching overview
      4m 56s
    2. Viewing and creating branches
      2m 57s
    3. Switching branches
      2m 58s
    4. Creating and switching branches
      4m 53s
    5. Switching branches with uncommitted changes
      3m 26s
    6. Comparing branches
      4m 28s
    7. Renaming branches
      2m 28s
    8. Deleting branches
      4m 18s
    9. Configuring the command prompt to show the branch
      9m 11s
  12. 28m 32s
    1. Merging code
      3m 11s
    2. Using fast-forward merge vs. true merge
      6m 49s
    3. Merging conflicts
      7m 26s
    4. Resolving merge conflicts
      7m 5s
    5. Exploring strategies to reduce merge conflicts
      4m 1s
  13. 14m 34s
    1. Saving changes in the stash
      4m 5s
    2. Viewing stashed changes
      2m 39s
    3. Retrieving stashed changes
      4m 24s
    4. Deleting stashed changes
      3m 26s
  14. 1h 5m
    1. Using local and remote repositories
      6m 38s
    2. Setting up a GitHub account
      5m 39s
    3. Adding a remote repository
      4m 0s
    4. Creating a remote branch
      4m 3s
    5. Cloning a remote repository
      4m 26s
    6. Tracking remote branches
      4m 5s
    7. Pushing changes to a remote repository
      5m 8s
    8. Fetching changes from a remote repository
      5m 47s
    9. Merging in fetched changes
      4m 50s
    10. Checking out remote branches
      3m 22s
    11. Pushing to an updated remote branch
      2m 6s
    12. Deleting a remote branch
      3m 8s
    13. Enabling collaboration
      3m 40s
    14. A collaboration workflow
      8m 43s
  15. 16m 23s
    1. Setting up aliases for common commands
      5m 14s
    2. Using SSH keys for remote login
      2m 56s
    3. Exploring integrated development environments
      1m 4s
    4. Exploring graphical user interfaces
      4m 32s
    5. Understanding Git hosting
      2m 37s
  16. 55s
    1. Goodbye
      55s

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Git Essential Training
6h 26m Beginner Aug 24, 2012

Viewers: in countries Watching now:

The course shows how to use Git, the popular open-source version control software, to manage changes to source code and text files. Using a step-by-step approach, author Kevin Skoglund presents the commands that enable efficient code management and reveals the fundamental concepts behind version control systems and the Git architecture. Discover how to track changes to files in a repository, review previous edits, and compare versions of a file; create branches to test new ideas without altering the main project; and merge those changes into the project if they work out. The course begins by demonstrating version control in a single-user, standalone context, before exploring how remote repositories allow users to collaborate on projects effectively.

Topics include:
  • Exploring the history of version control
  • Installing Git on Mac, Windows, and Linux
  • Initializing a repository
  • Writing useful commit messages
  • Understanding the Git three-tree architecture
  • Tracking when files are added, edited, deleted, or moved
  • Viewing change sets and comparing versions
  • Undoing changes and rolling back to previous versions
  • Ignoring changes to select files
  • Creating and working with code branches
  • Merging branches and resolving merge conflicts
  • Stashing changes for later
  • Working with hosted repositories and remote branches
  • Developing an effective collaboration workflow
Subject:
Developer
Software:
Git GitHub
Author:
Kevin Skoglund

Writing commit messages

In this movie I want us to talk about writing commit messages and the best practices for doing that. Now in the last movie we did our first commit, and we gave it a really simple single-line commit message that was just initial commit, pretty bland and boring and even worse, it doesn't really describe what we were doing. What you really want to do is have a commit message that describes the changes that you're making in that commit set, so added file to project, that would be more descriptive saying that we added this first file. That you added the JavaScript to something, that you were fixing a bug.

We are labeling what we were doing in this change set so when we come back and look at it later, we can just look at the commit message and know what's inside, what's contained in that set. So we want to have good descriptive commit messages. There are also some other best practices that we should follow. We want to start with a short single-line summary, less than 50 characters, keep it short. Optionally, we can follow that by a blank line and then a more complete description. Now if you are just making a tiny little change, a single-line summary will do it, but if you're committing a change that has lots of changes, that take place in lots of files, it might be worthwhile to have a more complete description.

Now the way we were doing it before from the single command line, that's a little tricky to do inside those double quotes, but we can also use a text editor to make these commit messages well, and that makes it easier to do multiline commit messages. Even then you want to keep those additional lines to less than 72 characters, and that's because different people may be looking at your commit log from different types of tools, they may be using Mac or Windows, viewing it on the web, graphical user interfaces, they may be receiving this commit information via email, so we want to limit it to 72 characters. And you want to write commit messages in the present tense, not in the past tense, you are labeling what this commit does, not what you--as the creator--were doing.

Label what it does. This fixes a bug, not I fixed a bug. It's not about you, it's about what this commit is. If you need to have bullet points that describe what happens you usually use asterisk or hyphens, and you can add ticket tracking numbers from bugs or support requests or develop a shorthand for your organization. So maybe you put, for example, in square brackets at the beginning of your message that you are messing with the CSS or the JavaScript or maybe you label all bug fixes with bugfix:, or put a tracking number in the front letting it know what sort of support request ticket it goes with.

These kinds of decisions are really the personal preferences that you or your organization will need to decide on. But it's a good idea to pick standards like this and then stick with them and get everyone to agree to it so that everyone working on the repository is using the same set of conventions for their commit messages. So you want to be clear and descriptive, so, for example, Bad: "Fix typo", would be an example of a bad commit that doesn't really tell what's going on. A good example would be "Add missing > in project section of HTML" much more descriptive of what we were doing, what was going on, what is the typo, what were we in here trying to fix.

Bad: "Update login code" that's pretty general, a good example "Change user authentication to use Blowfish", right, much more descriptive about what was going on and what we were doing with this change. Again, providing good labels on the outside of the envelope and then another bad example would be to include other comments in there that really aren't about the commit, so "Updates member report, we should discuss if this is right next week". Well, this commit is going to live in our repository potentially for years and years and years having a comment that that says we should discuss if this is right next week.

This isn't email, right, this in not a way to communicate with our team members, we can do that using other tools. What we want to do here is just provide a good label for what's inside the commit. So let's take a look at an example of one good commit. So here's an example of a good commit message, it's got a tracking number, this is the convention that this company is going to use for tracking support tickets, t23094 - Fixes bug in admin logout. That's a little bit vague, but we've got something underneath it that gives it more description, When an admin logged out of the admin area, they could not log in to the members area because their session :user_id was still set to the admin ID.

This patch fixes the bug by setting session :user_id to nil when any user logs out of any area. Notice that it describes what the problem was and then describes what the solution was as well. So it's all there. If we come, and we just look at this, we don't have to actually look at the code, and we have a good idea of what the creator of this commit was trying to do. It's a good label on the commit to let us know what it's going to do when we add this change set to the project. Now I mentioned that you should keep the first line to less than 50 characters and then subsequent lines to less than 72 characters.

Just as a reference, the longest line in this commit is about 60 characters wide. So that gives you an idea of how much you can fit on a line, you can go a little further than this, this is about 60 characters wide, and then you just need to hit a Return, and then you can keep typing. So hopefully right here from the start, I can get you thinking about what a good descriptive commit message is so that all of our commits will be well labeled. That's going to be really important with Git, because remember Git works with these commit snapshots and allows us to exchange them between repositories. So it's very important that we have well labeled commits so that if Bob makes a commit and then Mary is thinking about incorporating that commit into her project, she can look at it, see what that commit is, and decide to merge it into her project so that it becomes part for her project as well.

So having well-labeled commits is really important. In the next movie we'll take a look at how we can look at the log of previous commit messages.

Find answers to the most frequently asked questions about Git Essential Training.


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Q: In the Chapter 10 movie "Configuring the command prompt to show the branch," when I type the function "__git_ps1," I do not get the expected result.
A: The function "__git_ps1" was recently moved to a new file, .git-prompt.sh, as described here: https://github.com/git/git/commit/af31a456b4cd38f2630ed8e556e23954f806a3cc.

We will update the video. In the meantime, you may do the same steps you do for .git-completion.bash, but a second time using ".git-prompt.sh" as shown here: https://github.com/git/git/blob/master/contrib/completion/git-prompt.sh.
Q: When I use the code the instructor advises in the above video ("git config
--global user.name "Nelda Street"), I still get an "Illegal Instruction"
error. I have OS 10.6.8. Am I doing something wrong?
A: The current installer version of git isn't compatible with older Mac OS versions.
 
https://code.google.com/p/git-osx-installer/issues/detail?id=96
 
The workaround solutions people offer are:
 
1. To add "-mmacosx-version-min=10.6" as described here:
https://stackoverflow.com/questions/14268887/what-is-the-illegal-instruction-4-error-and-why-does-mmacosx-version-min-10
 
https://stackoverflow.com/questions/10177038/illegal-instruction-4-shows-up-in-os-x-lion
 
2. Or to use the version of git that comes with Xcode, or to use homebrew to install git instead.
http://superuser.com/questions/697144/installed-git-not-sure-how-to-get-it-working
 
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