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Exploring tree listings

From: Git Essential Training

Video: Exploring tree listings

In this movie, we are going to apply what we just learned in the last movie about how to refer to commits, and we are going to use it to be able to look at the tree listings. Remember that I told you that a tree is a lot like a directory on your file system. If I am in Unix, and I want to get a list of the current files that are in the directory I am in right now, I use the ls command for list, ls -la is a set of options that formats it so that it runs in a nice vertical list with all of the file names, including file names that start with a dot over on the right side.

Exploring tree listings

In this movie, we are going to apply what we just learned in the last movie about how to refer to commits, and we are going to use it to be able to look at the tree listings. Remember that I told you that a tree is a lot like a directory on your file system. If I am in Unix, and I want to get a list of the current files that are in the directory I am in right now, I use the ls command for list, ls -la is a set of options that formats it so that it runs in a nice vertical list with all of the file names, including file names that start with a dot over on the right side.

Now in Windows, you can do something similar with the dir command, but I want to stick with the ls of Unix for a second, because in Git, it's something very similar. To list out a tree, we use git ls-tree, listing the tree, and then what we pass in after that is a tree-ish. In fact, before we do it, let's take a look at the Help documentation, and notice right where it talks about how to use it, it says, get ls-tree, there is a whole bunch of options we can pass in and then after that it won't say tree-ish. So there it is. I am not making it up. That's the word for it, and it's a reference to the tree.

So let's try that, git ls-tree, and now we need a tree-ish. Well, one of the one is we can refer to the tree, is to use the HEAD that will point to the tip of the currently checked out branch, and it will return the list of files at that point. That's what's in the HEAD. Those are the files that are in the repository at that point, so that's what the repository thinks is the current set of files. If I were to check this out, brand new, from the repository, these are the files it would give me. Now those don't exactly match what I had in working directory because my working directory has some files that I have used gitignore on.

So you can play around and try out some different tree-ishes, so let's do git ls-tree master. That points to the exact same thing because we have the master branch checked out right now, so HEAD points to the tip of that, we are getting the exact same results. Let's take a look inside a directory there, we can pass in a file path after that, so git ls-tree master, and let's ask it for assets with the slash after it. So the contents of the assets directory, and it comes up and tells us the files that are inside that directory.

Now let's try going back one commit. I don't know if you remember, but one commit back is when we actually created this pdfs folder, that's when we added it. So unless you made other commits, in which case you may need to go back further, but one commit back will now show us that directory in its previous state. So in the commit before that, there was no pdfs folder, in the commit after it, now there is a pdfs folder. One more thing I want to show you, notice that each of these entries over here on the left, it tells you that everything is either a tree or a blob. A blob is a file. It can be any kind of file that's stored there.

It can be text file, an image, anything, they are all stored as a blob. If it's not a blob, then it's a tree and guess what a tree is? A tree is a directory. So we are inside a tree because we had a tree- ish that pointed us to a tree and then inside that tree are other trees. Well, that three has an object number, it goes with it. So we can grab the first part of that, copy it, and then we can say, well git ls-tree and pass in that SHA, that's a tree-ish that points to it and look what it gives us.

It gives us back the exact same thing that we had here, the only difference is that it doesn't prefix it with the assets directory because we have already told it it's the tree. This was telling us we were starting with master and then looking inside assets, so it listed assets for us. Here were starting at assets so it doesn't give us the prefix there. So try it out, play around little bit and get comfortable with it and make sure that you understand the things that we learned in the last movie about the different tree-ishes and the way that we can reference different trees this way.

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This video is part of

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Git Essential Training

89 video lessons · 30310 viewers

Kevin Skoglund
Author

 
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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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