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Working alone

📌 Learning objectives:

  • Learn to use Git alone

Local first

With Git, everything is local, remote operations are only for sharing. You do not have to be connected to Internet or any server to work.

Git only tracks files

Git has no notion of directories, only files are tracked (technically, contents).

Git help

git help gives general guidelines on Git usage. It can also be applied on a specific command:

$ git help [command]

Configuring your identity

$ git config --global user.name "Your name here"
$ git config --global user.email "[email protected]"

Git stores global configuration settings in ~/.gitconfig.

Creating a repository

Move to your working directory and initialize a Git repository, containing the whole project history:

$ cd /path/to/project
$ git init

Initialized empty Git repository in /path/to/project/.git/

Running git init in an existing repository will not overwrite things that are already there.

🚀 Hands-on

  1. Configure your identity
  2. Create a Git repository named "git-training"
  3. Inspect its content with the Finder/File viewer/Explorer

What's up?

git status gives you many information about your project, i.e. about the working directory and Git repository:

$ git status
On branch master

Initial commit

nothing to commit (create/copy files and use "git add" to track)

Adding files

$ touch mars.txt
$ git add mars.txt
$ git commit -m "Add mars.txt"
  • git add: adds files to the staging area
  • git commit: commits the state of the staging area

Staging area

The staging area is a place where we can group files together before we "commit" them to Git.

Git add

git add adds files to the staging area.

  • When files are new, it enables tracking on these files
  • When files are tracked, only the changes are added

Git commit

git commit makes the changes of the staging area part of the local Git repository. A commit message is required.


Writing good commit messages

Capitalized, short (50 chars or less) summary

More detailed explanatory text, if necessary.  Wrap it to about 72
characters or so. In some contexts, the first line is treated as the
subject of an email and the rest of the text as the body. The blank
line separating the summary from the body is critical (unless you
omit the body entirely); tools like rebase can get confused if you
run the two together.

Write your commit message in the imperative: "Fix bug" and not "Fixed
bug" or "Fixes bug." This convention matches up with commit messages
generated by commands like git merge and git revert.

Further paragraphs come after blank lines.

A Note About Git Commit Messages

On commit identifiers

Each commit is identified by a hash (SHA).

$ git show f7ff9ec81552261105ce8573c14dd46d8a8c2aad

It is a long id but you can usually type the first chars only:

$ git show f7ff9

HEAD is a special reference to the most recent commit.

Git log

git log displays all the commits of your project. You can also pass a filename to filter the commits.

$ git log
commit 2d95be7716feb718d0cd623eb0c778bbf7f512c4
Author: William Durand <[email protected]>
Date:   Sun Sep 17 21:17:04 2017 +0200

    Add mars.txt

commit 4b24c727e6754b0fcc3245cd53880a100f58981f
Author: William Durand <[email protected]>
Date:   Sun Sep 17 21:16:50 2017 +0200

    Add README.md

Viewing a specific commit

git show <commit> displays the information of a given commit or the most recent commit if none specified:

$ git show 4b24c727e6754b0fcc3245cd53880a100f58981f
commit 4b24c727e6754b0fcc3245cd53880a100f58981f
Author: William Durand <[email protected]>
Date:   Sun Sep 17 21:16:50 2017 +0200

    Add README.md

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e69de29

🚀 Hands-on

  1. Create a file named README.md
  2. Add it to the staging area
  3. Verify that it worked
  4. Commit this file with the -m option
  5. Create a file named mars.txt
  6. Commit it with git commit (no option)

Moving files

$ git mv some-file.txt better-name.txt
$ git status
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	renamed:    some-file.txt -> better-name.txt
$ git commit -m "Rename some-file.txt to better-name.txt"

Removing files

$ git rm better-name.txt
rm 'better-name.txt'
$ git status
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	deleted:    better-name.txt
$ git commit -m "Delete better-name.txt"

🚀 Hands-on

  1. Create a file named baz.txt
  2. Commit it
  3. Rename this file to venus.txt
  4. Commit it
  5. View the log for this file

Git checkout

git checkout allows to restore an old version of a file:

$ git checkout <commit> <filename>

It is useful to discard changes in the working directory:

$ git checkout -- <filename>

Git reset

git reset can be used to unstage a file:

$ git reset HEAD <filename>
$ git reset -- <filename>

The lifecycle of files

Updating the status of a file

🚀 Hands-on

  1. Create a new file nope.txt
  2. Add it to the staging area
  3. Undo the previous step and see what happens
  4. Update the content of venus.txt
  5. Add this change to the staging area
  6. Undo the previous step and see what happens
  7. Update the content of venus.txt and commit

Git diff

git diff <commit> shows the difference between the last commit and unstaged changes in the current project:

$ git diff
diff --git a/venus.txt b/venus.txt
index 257cc56..3bd1f0e 100644
--- a/venus.txt
+++ b/venus.txt
@@ -1 +1,2 @@
 this is about venus
+bar

Staged changes

To see the difference between staged changes and the previous version of the repository, use:

git diff --staged

🚀 Hands-on

  1. Modify the content of your README.md file
  2. Review your changes
  3. Commit them

Ignoring things

Git can be configured with a special .gitignore file to mask certain files. You can use wildcards, regular expressions and exact filenames.

Gitkeep

Sometimes, you want to exclude all files of a given directory but keep this directory under version control.

Commit a .gitkeep file into it before ignoring it.

🚀 Hands-on

  1. Create a .gitignore file and commit it
  2. Ignore the directory named result/
  3. Create this directory and add files into it
  4. See what happens
  5. Keep this result/ directory under version control

Git stash

git stash is a nice Git feature that allows you to put a set of changes on hold and get back to them later.

  • git stash takes the state of the staging area and saves it as a "draft"
  • git stash pop: apply the latest "draft" and remove it from the list
  • git stash list: list all your "drafts"