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Git Essential Training
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Merging in fetched changes


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Git Essential Training

with Kevin Skoglund

Video: Merging in fetched changes

In the last movie, we used git fetch in order to sync up origin/master with the master branch on the remote repository, but we noticed that while it brought those commits down into origin/master, it didn't bring them into master on our local repository. All it did was get origin/master in sync. If we want those changes to be incorporated into our master branch, we need to do that additional step ourselves, and that's we are going to learn how to do in this movie, using merges. Now you will recall earlier that I told you that origin/master is just a branch like any other branch.
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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

Merging in fetched changes

In the last movie, we used git fetch in order to sync up origin/master with the master branch on the remote repository, but we noticed that while it brought those commits down into origin/master, it didn't bring them into master on our local repository. All it did was get origin/master in sync. If we want those changes to be incorporated into our master branch, we need to do that additional step ourselves, and that's we are going to learn how to do in this movie, using merges. Now you will recall earlier that I told you that origin/master is just a branch like any other branch.

It's a remote branch, the only thing that really differentiates it from the branches that we normally work with is the fact that we can't check it out, other than that it's really the same, and it make sense that we can't check it out, because Git really needs to be able to keep it in sync with what's on the remote server, and it doesn't want us getting in the way of that. If we check that out, we might make a commit to it, and that would just confuse things. Instead, we have our branches that we are in charge of, but Git is going to remain in charge of origin/master and make sure that it mirrors what's on the remote. But other than the fact that we can't check it out, it is exactly like any other branch.

That's an important point to remember, because we are going to merge with it just like any other branch. In this illustration, you can see that the remote server has five commits in it, and a fetch has taken place, because origin/master is perfectly in sync with what's on the remote server. Our master branch however is two commits behind, so it needs to have those two commits added to it, and the process that we do that is by merging, and the merging works exactly like everything that we learned about merging before in the merging chapter. The only difference is that we are using a branch called origin/master, instead of some other branch name that we worked with before.

But in this particular illustration, if we were to do a merge right now, master would do a fast-forward merge just like the fast forward merges that we learned about previously. Now if we made additional commits on the master branch, in the meantime, then those would need to be merged in, and we would have a merge commit that would join those together just like we did before. And of course, it's also possible that the 923ea commit that's in origin/master has something that conflicts with what we have got in ba8ce in our master branch, and if it conflicts, well just like with the normal merge, we have got to resolve those conflicts.

And we resolve those conflicts in the exact same way, and we commit the result into our merge commit. Let's try it out. Okay, notice that I am inside my lynda_ version folder, and I am on the master branch. First, let's just remind ourselves where our branches are, we have git branch, and we will use the -a option so that we see all of them. So what I want to do is I want to take master and merge it with origin/master. We can also just do a diff if we want first to find out what's the difference, master origin/master, and it tells us, so we can see what those changes are.

Okay, now that I know it's different, yes, I do want to go through with that merge. So git merge and just like before, normally we would type a branch name, now we are going to type origin, and then the branch name. So merge in origin/master, so I will hit Return, and you can see sure enough it tells us right here that it was a fast-forward merge, and now get log --oneline, we'll do three lines for the master branch, and you see that now the change has appeared there. Now let's just look at the diagram again and just make sure that something is super clear you, when we do a merge, we are merging with origin/master.

Our local version, that's where we are merging in, we are not going back up to GitHub to see what's there. So when we do a merge, we always want to make sure we do a fetch first. Fetch, then merge. Now it's possible that new things might have come in, in the meantime of the remote server, we will worry about those later, but we do want to do our best to be as up-to-date as possible. So now that we understand this process, git fetch, git merge. That's the process that we are going to go through. I want you to know about a shortcut called git pull. Git pull is equal to git fetch+git merge.

It does it all in one step. It goes out there, finds the latest, brings it down and merges it into your current branch, all in one big shortcut. Now there are lots of pros and corns to using git pull. First, it's super convenient. So a lot of people use it by default for that reason. The bad part is, that for beginners, it obscures the fact that you are actually doing this two step process, and I think that a lot of people who use git pull a lot, forget about doing git fetch and git merge. They don't really realize that that's what's it doing for them under the hood, and then sometimes when things go wrong with git pull, it's hard for them to understand what actually went wrong and what happened and how to fix it.

If you use git fetch+git merge, it's much harder for those kinds of problems to arise, because it's much clear what went wrong and how to fix it. So my recommendation is to try and use git fetch and git merge for a while, until you feel like you've got the hang of it and then if you know that what you really want is just git fetch and pull down the changes, then you can try using git pull.

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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