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Git Essential Training
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Comparing branches


From:

Git Essential Training

with Kevin Skoglund

Video: Comparing branches

In this movie, we're going to talk about how we can compare branches. Now we saw in the last chapter, we talked about navigating the commit tree, so we could use the git diff command in order to compare two different tree-ish objects. And at the time, I told you that a branch was one of the tree-ish's that we can pass in, but we didn't have any branches back then. Now we have some branches so let's try comparing them. Use git diff, and then we just pass in the names of the branches. Let's remind ourselves that those branches are real quick. There is a list of our branches, and I'm on the shorten title branch, let's say git diff master..new_feature.
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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

Comparing branches

In this movie, we're going to talk about how we can compare branches. Now we saw in the last chapter, we talked about navigating the commit tree, so we could use the git diff command in order to compare two different tree-ish objects. And at the time, I told you that a branch was one of the tree-ish's that we can pass in, but we didn't have any branches back then. Now we have some branches so let's try comparing them. Use git diff, and then we just pass in the names of the branches. Let's remind ourselves that those branches are real quick. There is a list of our branches, and I'm on the shorten title branch, let's say git diff master..new_feature.

So I'm going to compare master with new feature by using that range operator in between, dot dot. So master compared to new_feature, and it comes up and tells me what are the differences between the tip of master and the tip of new_feature, the most recent commits there. That snapshot. So I now can very easily see what changed between the two versions. Try it again with master and shorten_title. So there is what changed there. That includes those changes that were made in the new feature branch, remember because shorten title is a branch off of new_features, so it has all of those changes as well.

And of course, we can do the intermediary step git new_feature compared to shorten title. The order of these doesn't really matter. Let me just show you, let's do that one again, and now let's just flip them around, let's do git diff shorten_title..new_feature. It'll show us the exact same diff, it just flipped them around. It changed which one was the a or minus and which one is the b or plus. So that's all it did. Typically the one that's further back in time, you would make the one that comes first, and the one that comes later would be the one that made second.

But time can be kind of tricky when you start working with branches and different commits are being made at different places. So it really is just about which one you want to be the old state, and which one you want to be the new state. Another nice feature that we can use with diff is colorwords option. So let's go with this one, the new_ feature..shorten_ title, and let's add in --color-words, with a space. Now it comes up and shows with the same diff, but it shows it to us all on oneline. So that might be a little clear for you as to what changed, instead of having the two lines, one above each other.

It's really matter of personal preference for which one you like better. Now of course, what we are passing in here is not just a branch, we are passing in a tree-ish. We talked about tree-ishs. A tree-ish can be a lot of things, it can even include the ancestors. So for example, I can compare new_ feature with the previous commit to the HEAD of shorten_title. So go to shorten_title, and it's not the last the commit, it's the commit right before that, that I want to compare it to. And we can see that what changed was I took out the words, welcome to.

There is one more important way that we can compare branches, and that's that we can find out, whether one branch completely contains another branch or not. That is whether or not everything in it has been merged into the current branch. We do that by not using the diff tool but using git branch with the dash dash merged option after it. That will show us all branches that are completely included in this branch. So in this case we're on the shorten_title branch, all of the commits that are in new_feature are also in shorten_title, all of the commits that are in master are also in shorten_title.

What that lets us know is that we can actually delete new feature if we wanted to and shorten_title wouldn't be affected. Shorten_title has all of those commits in it. Let's try switching to different branch, git checkout new_feature, surround it again, git branch merged. Now it says, all right, new feature doesn't have all of the commits that are in shorten_title. Shorten_title has some things that are not merged into here yet, we would need to do a merge to get those changes into new feature first. What it actually does is it goes back up the ancestor chain of the new_feature branch to see does it have the tip of master in it.

If it has that final commit of master, then it has all of the ancestors as well. It does not have the final commit of shorten_title so it doesn't list it here. And just for good measure, let's do checkout master, and we will do the same thing there, and you see that master doesn't contain those changes that are in new_feature and shorten_title. So well, it's not strictly speaking comparing branches, the same way that diff does, I think it's important way to get some information about the comparison of the content of what is in each of the branches. Those come in very handy soon, when we start trying to delete branches.

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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