Lecture 2: Basic commands

Introduction to Git --- Fall 2024 # Lecture 2: Basic commands   ![TOC](https://www.hpc2n.umu.se/sites/default/files/umu-logo-left-se.png =200x) ![](https://www.hpc2n.umu.se/sites/default/files/logo-hpc2n-git-course.png =90x) ![](https://www.hpc2n.umu.se/sites/default/files/conferences-courses/2023/Uppsala_Universitet-logo-2E2D20E6B3-seeklogo.com.png =100x) ![](https://www.hpc2n.umu.se/sites/default/files/conferences-courses/2023/naiss-narrow.jpg =200x) Slides: https://hackmd.io/@git-fall-2024/L2-commands ---  <style type="text/css"> .reveal p { text-align: left; } .reveal ul { display: block; } .reveal ol { display: block; } </style> ## Getting help ```console $ git help <command> $ man git-<command> $ git help commit GIT-COMMIT(1) Git Manual GIT-COMMIT(1) NAME git-commit - Record changes to the repository SYNOPSIS git commit [-a | --interactive | --patch] [-s] [-v] [-u<mode>] [--amend] [--dry-run] [(-c | -C | --fixup | --squash) <commit>] [-F <file> | -m <msg>] [--reset-author] [--allow-empty] [--allow-empty-message] [--no-verify] [-e] [--author=<author>] [--date=<date>] [--cleanup=<mode>] [--[no-]status] [-i | -o] [-S[<keyid>]] [--] [<file>...] DESCRIPTION ``` ---  ## Creating a repository from scratch In case you want to start a project from scratch called **myproject**: ```bash $ mkdir myproject $ cd myproject $ git init Initialized empty Git repository in .../myproject/.git/ ``` this will create a folder called *.git* in the current folder which contains the Git-related files. ---  We can now ask about the status of the repository: ```bash $ git status On branch master No commits yet nothing to commit (create/copy files and use "git add" to track) ``` ---  ## Creating a repository by cloning an existing repository Use the command: ```console $ git clone repository_location path_where_it_will_be ``` *repository_location* is the path of the Git repository (if it is in your local machine) or a URL if it is on the internet. *path_where_it_will_be* is the path for the cloned repository. ---  ```console $ git clone https://github.com/aliceuser2020/my-first-project.git ./my-project Cloning into 'GitCourse/Alice/my-project'... remote: Enumerating objects: 3, done. remote: Counting objects: 100% (3/3), done. remote: Total 3 (delta 0), reused 0 (delta 0), pack-reused 0 Unpacking objects: 100% (3/3), done. Checking connectivity... done. $ cd ./my-project $ git status On branch master Your branch is up-to-date with 'origin/master'. nothing to commit, working directory clean ``` ---  ## Stages of files ![](https://www.hpc2n.umu.se/sites/default/files/git-folders2.png =780x) ---  ## Monitoring the differences in files Differences or changes in files can be seen with the command ```console $ git diff ``` This command supports different options. ---  ## Adding files' modifications After initializing the repository, we decide to create a file called *first.txt* ```console $ echo "This is my first file" > first.txt ``` If we ask about the status of the repository we will see the following message, ---  ```console $ git status On branch master No commits yet Untracked files: (use "git add <file>..." to include in what will be committed) first.txt nothing added to commit but untracked files present (use "git add" to track) ``` ---  ![](https://www.hpc2n.umu.se/sites/default/files/git-folders-changes-wd.png) ---  We can now add the *first.txt* file to the staging area: ```console $ git add first.txt ``` and then check the status of the repository: ```console $ git status On branch master No commits yet Changes to be committed: (use "git rm --cached <file>..." to unstage) new file: first.txt ``` ---  ![](https://www.hpc2n.umu.se/sites/default/files/git-folders-changes-sa.png) ---  ## Unstaging files' modifications part I If you want to unstage the changes (maybe you are not convinced of them) type the line suggested by Git: ```console $ git rm --cached first.txt ``` Notice that Git suggests this command because the repository is brand-new and nothing has been committed yet. ---  ## Committing changes Once the changes are staged, they can be commited with the command ```console $ git commit ``` this will open a window of the default text editor in your system (in this case **Vim**) ---  ```console First commit in myproject # Please enter the commit message for your changes. Lines starting # with '#' will be ignored, and an empty message aborts the commit. # # On branch master # # Initial commit # # Changes to be committed: # new file: first.txt # ``` write a commit message and upon saving the file the changes will be committed. ---  ```console $ git commit [master (root-commit) 3a7625b] First commit in myproject 1 file changed, 1 insertion(+) create mode 100644 first.txt ``` the status after committing is ```console $ git status On branch master nothing to commit, working tree clean ``` ---  Fast (lazy?) commit option: ```console $ git commit -a -m "Commit message" ``` this command will add all files that were modified (and tracked) and commit them with the quoted message. ---  ![](https://www.hpc2n.umu.se/sites/default/files/git-folders-changes-lb.png) ---  ## Unstaging files' modifications part II Imagine that after doing the first commit for *first.txt* file, you modify this file and stage it (*git add first.txt*). If you check the status the output will be (version 2.25.1): ```console On branch master Changes to be committed: (use "git restore --staged <file>..." to unstage) modified: first.txt ``` ---  For versions before 2.23 the status would look like: ```console On branch master Changes to be committed: (use "git reset HEAD <file>..." to unstage) modified: first.txt ``` ---  Git suggests a different way to unstage the file as we saw before, because now there is a HEAD pointer. ---  ```console $ git restore --staged filename ``` unstages the changes made to *filename*. From the website https://git-scm.com/docs/git-restore: THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE. ---  ```console $ git reset HEAD filename ``` is an old command for unstaging, ```console $ git rm --cached filename ``` with this command Git will untrack *filename* (staging for removal) leaving the file in the working directory ---  ## Content of a commit message - why is this change needed? - how is the problem approached? - are there side effects? - write structured text (~70 characters) - one can include the ticket numbers for related issues for instance (#1112) **Important:** check that the code works before commiting. Here, test cases are very handy. Git kurz & gut, O'Reillys, Nina Siessegger. ---  ## Reverting to the previous commit If you made a commit and you regret it later, you can revert the changes to the previous commit with the command: ```console $ git revert HEAD ``` ---  ## Adding multiple files In case you want to add multiple files, that follow a pattern, at the same time you can use Linux-type wild cards. As an example, we can add the files *file1.txt, file2.txt, file3.txt* at once with the commands (equivalent for this test case): ```console $ git add file?.txt $ git add file[1-3].txt $ git add *.txt ``` ---  If we want to add all the files for staging we can do: ```console $ git add -A (all files including those in the parent folder) $ git add . (all files in the sub-folders) ``` ---  ## Renaming files/folders Imagine that you want to change the name of the file *first.txt* to *Readme.txt*, in this case you can use the command: ```console $ git mv oldfilename newfilename $ git mv first.txt Readme.txt ``` ---  Although there is not feedback from the command the status of the file has now changed ```console $ git status On branch master Changes to be committed: (use "git restore --staged <file>..." to unstage) renamed: first.txt -> Readme.txt ``` you can now commit the changes. Renaming files, instead of creating new ones, can help you to keep a consistent history of the files. ---  ## Moving files Similar to the **mv** Linux command, the **git mv** command can be also used to move a file to a different location: ```bash $ git mv filename newlocation $ git mv first.txt src/ $ git status On branch master Changes to be committed: (use "git restore --staged <file>..." to unstage) renamed: first.txt -> src/first.txt ``` ---  ## Removing files If some file is not useful any longer and we want to delete it from our repository, we can issue the command, ```bash $ git rm location/filename $ git rm src/first.txt $ git status On branch master Changes to be committed: (use "git restore --staged <file>..." to unstage) deleted: src/first.txt ``` Sometimes it is more convenient to rename files instead of deleting them to keep the history more consistent. ---  ## Ignoring files If you want to ignore some files in your repository, for instance, temporary (.tmp) or binary (.bin) files. One way to accomplish this is by creating a file called **.gitignore** in the repository with some rules with a Linux-type wild cards syntax ---  ```shell $ cat .gitignore *.tmp *.bin ``` then, you will have to commit the **.gitignore** file as usual. ---  One caveat of using a **.gitignore** file is that it will be shared with all the collaborators. One can instead use the local exclude file in *.git/info/exclude* to define the rules. This file won't be shared. ```console # $ git ls-files --others --exclude-from=.git/info/exclude # Lines that start with '#' are comments. # For a project mostly in C, the following would be a good set of # exclude patterns (uncomment them if you want to use them): # *.[oa] # *~ *.tmp *.bin ~ ``` ---  ## Generating aliases The following command shows a graph of the commits' tree in an organized way: ```java $ git log --all --decorate --oneline --graph ``` This command is too long to type/remember. Git allows you to create shortcuts/aliases for commands: ```java $ git config --global alias.shortcut <git command> $ git config --global alias.graph "log --all --graph --decorate --oneline" ``` ---  In this way, you can use a customized **git graph** command: ```java $ git graph * 39ecba2 (HEAD -> master) Fourth commit * 3cd651b Third commit * 7dce2ff Second commit * 1f2cdcc First commit ``` A second way to generate an alias is by adding it to your *.bashrc* file: ```java alias graph="git log --all --decorate --oneline --graph" ``` which will make the command *graph* available on the command line. ---  # Intermediate/ Advanced commands ---  ## Adding files' modifications interactively Suppose we create an empty file, stage it, and commit the changes as follows: ```shell touch first.txt git add first.txt git commit -m "first file" ``` Now, we add a couple of lines to our file *first.txt* and now it looks like ```shell This is my first file * TODO list * Summary ``` ---  The status command tells us that we did some modifications to the file: ```console On branch master Changes not staged for commit: (use "git add <file>..." to update what will be committed) (use "git restore <file>..." to discard changes in working directory) modified: first.txt no changes added to commit (use "git add" and/or "git commit -a") ``` ---  Let's suppose that the new text (5 lines) refer to different topics: *TODO list* and *Summary*. Then, it would be better to have them in different commits. We can add the modifications interactively: ---  ```console $ git add -p first.txt ``` ```console diff --git a/first.txt b/first.txt index e69de29..96dd9a2 100644 --- a/first.txt +++ b/first.txt @@ -0,0 +1,5 @@ +This is my first file + +* TODO list + +* Summary (1/1) Stage this hunk [y,n,q,a,d,e,?]? ``` choose the **e** edit option to enter the editing mode. ---  ```console # Manual hunk edit mode -- see bottom for a quick guide. @@ -0,0 +1,5 @@ +This is my first file + +* TODO list + +* Summary # --- # To remove '-' lines, make them ' ' lines (context). # To remove '+' lines, delete them. # Lines starting with # will be removed. ``` Because we don't want *Summary* in the first commit, we delete that line and save the file. ---  You can now take a look at the status of the file ```console $ git status On branch master Changes to be committed: (use "git restore --staged <file>..." to unstage) modified: first.txt Changes not staged for commit: (use "git add <file>..." to update what will be committed) (use "git restore <file>..." to discard changes in working directory) modified: first.txt ``` ---  Notice that the file first.txt has been partially staged. ![](https://www.hpc2n.umu.se/sites/default/files/git-folders-changes.png) ---  The difference between staged changes and the unstaged ones can be seen with: ```console $ git diff ``` the difference between staged changes and the previous commit with: ```console $ git diff --staged $ git diff --cached ``` ---  and the difference between the unstaged changes and the previous commit with: ```console $ git diff HEAD ``` At this point, you can commit the staged changes and later on stage and commit the remaining changes. ---  ## Amending commits The following command will modify your last commit by adding more content to it: ```shell $ git commit --amend ``` the flag *-m* will allow you to write a short message and *- -no-edit* will keep the message from the previous commit. Note: use this command in commits that haven't been pushed on public branches. This command modifies the history. ---  ## Simplifying commits Suppose that you have a series of commits which are close-related in your *local repo*: ```java $ git log --all --decorate --oneline --graph $ git graph * 39ecba2 (HEAD -> master) Fourth commit * 3cd651b Third commit * 7dce2ff Second commit * 1f2cdcc First commit ``` in this case, the three last commits are related and can be squashed into a single commit. ---  ```java $ git rebase -i HEAD~3 pick 7dce2ff Second commit pick 3cd651b Third commit pick 39ecba2 Fourth commit # Rebase 1f2cdcc..39ecba2 onto 1f2cdcc (3 commands) # # Commands: # p, pick <commit> = use commit # r, reword <commit> = use commit, but edit the commit message # e, edit <commit> = use commit, but stop for amending # s, squash <commit> = use commit, but meld into previous commit # f, fixup <commit> = like "squash", but discard this commit's log message # x, exec <command> = run command (the rest of the line) using shell # b, break = stop here (continue rebase later with 'git rebase --continue') # d, drop <commit> = remove commit # l, label <label> = label current HEAD with a name # t, reset <label> = reset HEAD to a label # m, merge [-C <commit> | -c <commit>] <label> [# <oneline>] # . create a merge commit using the original merge commit's # . message (or the oneline, if no original merge commit was # . specified). Use -c <commit> to reword the commit message. # # These lines can be re-ordered; they are executed from top to bottom. # # If you remove a line here THAT COMMIT WILL BE LOST. # # However, if you remove everything, the rebase will be aborted. # # Note that empty commits are commented out ``` ---  choose the option **s** (squash) ```java pick 7dce2ff Second commit s 3cd651b Third commit s 39ecba2 Fourth commit # Rebase 1f2cdcc..39ecba2 onto 1f2cdcc (3 commands) # # Commands: # p, pick <commit> = use commit # r, reword <commit> = use commit, but edit the commit message # e, edit <commit> = use commit, but stop for amending # s, squash <commit> = use commit, but meld into previous commit # f, fixup <commit> = like "squash", but discard this commit's log message # x, exec <command> = run command (the rest of the line) using shell # b, break = stop here (continue rebase later with 'git rebase --continue') # d, drop <commit> = remove commit # l, label <label> = label current HEAD with a name # t, reset <label> = reset HEAD to a label # m, merge [-C <commit> | -c <commit>] <label> [# <oneline>] # . create a merge commit using the original merge commit's # . message (or the oneline, if no original merge commit was # . specified). Use -c <commit> to reword the commit message. # # These lines can be re-ordered; they are executed from top to bottom. # # If you remove a line here THAT COMMIT WILL BE LOST. # # However, if you remove everything, the rebase will be aborted. # # Note that empty commits are commented out ``` ---  a text editor message will appear where you can type the message for the squashed commit: ```java # This is a combination of 3 commits. # This is the 1st commit message: Summary of three commits #Second commit # This is the commit message #2: #Third commit # This is the commit message #3: #Fourth commit # Please enter the commit message for your changes. Lines starting # with '#' will be ignored, and an empty message aborts the commit. # # Date: Mon Sep 21 16:48:36 2020 +0200 # # interactive rebase in progress; onto 1f2cdcc # Last commands done (3 commands done): # s 3cd651b Third commit # s 39ecba2 Fourth commit # No commands remaining. # You are currently rebasing branch 'master' on '1f2cdcc'. # # Changes to be committed: # modified: Commits.txt # ``` ---  Finally, we check the log file and see that we have now only two commits with the new commit message: ```console $ git log --all --decorate --oneline --graph $ git graph * 62f921f (HEAD -> master) Summary of three commits * 1f2cdcc First commit ``` Note: use this command in commits that haven't been pushed on public branches. This command modifies the history. ---  ## Git blame (Advanced) it displays information about the last modifications of authors line by line ```java git blame filename $git blame 1.basic-commands/README.md ^a18abd1 (Birgitte Brydsö 2021-09-28 12:21:06 +0200 9) - stage the file ^a18abd1 (Birgitte Brydsö 2021-09-28 12:21:06 +0200 10) - commit the changes dd5db248 (Pedro Ojeda-May 2021-11-02 10:53:01 +0100 11) - create a second file "Poem.md" without any text (hint: use touch command), stage and commit it ``` here we can see the commit, author, timestamp, line number and line content.