Git: Actual Guide With Actual Examples

Monday, 15 August 2016

Git is a free distributed revision control system for source code management (SCM). It is open source and designed to increase the speed and the efficiency on distributed and non-linear workflow projects. Additionally it improves its data integrity. You can download it from git-scm.com/downloads.

First things first

You need to get familiar to a few terms that will come up frequently. They are:

  • repository: also shortened as repo, it’s a directory where your project code will be managed and versionized. It can be local folder on your computer or it can be a storage space on an online host;
  • commit: it’s a command that create a “snapshot” of the current state of your repository in time, giving you a checkpoint to which you can analyze or restore your project to any previous state (other commits);
  • commit hash: it’s a SHA1 hash linked to a commit working as its id. Although its 40-digit-long size, you only need the 4 or 6 first chars to refer it;
  • branch: branches are separate areas of development where you can work without interfering to each other. It’s by this way that Git is collaborative. There’s at least one branch in your repo and you should never work in a repository which other person is working on. You create a branch for you instead;
  • staging area or index: a cache of files that you want to commit. An area where files added to index are enrolled;
  • staged files: files prepared for a commit, added to index;
  • unstaged files: files not prepared to commit, not added to index;
  • working directory: the root folder where you perform your coding;
  • working copy: the folders and files that you’re currently using. It’s always local;
  • snapshot: it’s a “time registration” of your project in time created by a commit. A “version”;
  • history: it’s a “book” that contains everything of all the registrations of your project since your gitted it.

Customizing Git configuration: git config

This command allows you to configure your Git installation globally or on an individual repository. It can define from user info to preferences to the behavior of a repository. Find below the most used git config commands.

git config user.name <name> and git config --global user.email <email> define author’s information that will be shown on commits and logs.


$ git config --global user.name Your Name
$ git config --global user.email your@email.com

You also can create a shortcut to git command (e.g. git stage as git add), using git config --global alias.


$ git config --global alias.stage add
$ git config --global alias.co commit
$ git config --global alias.cane "commit --amend --no-edit"

git co will work as git commit.

You can choose your preferred editor with git config --global core.editor <editor>, Git’s default one is vi.


$ git config --global core.editor "subl -n -w"

Creating a repo: git init [--bare]

To create a repository with a working directory where you can actually work, you simply need to use this command inside the directory:


$ git init
Initialized empty Git repository in ~/git_101/.git/

After creating it you will see that the directory contains a .git folder where all the git stuff goes in and you will work at the level where the .git folder is.

Bare repository is a git repository without a working directory, so you can’t work on it. Typically, when you are on a server, you have no need to have a working directory, and bare repositories are usually central repositories where all collaborators move their work to. It’s a way to synchronize efforts between multiple people.


$ git init --bare
Initialized empty Git repository in ~/git_101_bare/

Cloning an existing repo: git clone [--bare] <repo> [<directory>]

This command is similar to git init, but it clones a repo instead of creating one. Additionally it creates a remote called origin which represents where the repo was cloned from, sets up a local branch based on the remote’s active branch (generally master), and creates remote-tracking branches for all the branches in the repo.


$ mkdir git_102
$ git clone git_101 git_102
Cloning into 'git_102'...
done.

It works for bare repos as well:


$ mkdir gg
$ git clone --bare git@github.com:LeonardoCardoso/mvn-repo.git gg
Cloning into bare repository 'gg'...
remote: Counting objects: 24, done.
remote: Compressing objects: 100% (11/11), done.
remote: Total 24 (delta 1), reused 24 (delta 1)
Receiving objects: 100% (24/24), 282.70 KiB | 125.00 KiB/s, done.
Resolving deltas: 100% (1/1), done.
Checking connectivity... done.

Adding files to staging area: git add <file>

Let’s create the file new_file.txt. It has to be created inside the working directory where you initialised git. git add <file>


$ vi new_file.txt
$ git add new_file.txt

By this doing, our new_file.txt is on the staging area and ready to be committed. To add all files that are not staged, use:


$ git add .

Removing files from staging area: git rm [--cached] <file>

To remove a file from staging area and/or tracking, use git rm [--cached] <file>.


$ git rm new_file.txt

Caution: to remove all files, use:


$ git rm .

To remove file from version control and keep it in the working repository, use git rm --cached <file>.


$ git rm --cached new_file.txt

Committing a file: git commit [-m] [<message>]

Committing a file is like telling Git to create a snapshot of the state of you project. All the files you’ve added, modified and removed since the last commit will have their status updated with this new commit. A message can be added to describe briefly what was changed.

Let’s commit our new_file.txt that we have already added: git commit -m <message>.


$ git commit -m "Initial commit"
[master (root-commit) 13abdd5] Initial commit
    1 file changed, 1 insertion(+)
    create mode 100644 new_file.txt

You also have the option to open your editor on commit. Just use: git commit.


$ vi .gitignore
$ git add . gitignore
$ git commit

Editor will open. So you can add your message…


.gitignored added
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch master
# Changes to be committed:
#       new file:   .gitignore
#
[master 44e0174] .gitignored added
    1 file changed, 1 insertion(+)
    create mode 100644 .gitignore

.gitignore: A special file

.gitignore is a file that Git always looks before its commands. There you can tell git which files are not (and will be not) tracked. It’s a simple text file and you can use regular expressions to block more than one file at once.


$ vi .gitignore

Editor will open. So you can add your files which won’t be tracked anymore…


thisFileWillBeIgnored.txt
# file ignored
dir/
# entire directory ignored
anotherDir/starting*
# only files that start with "starting" inside anotherDir will be ignored
*.jar
# all jar files will be ignored

If a file is already being tracked, you need to remove it, so it won’t be tracked anymore. Otherwise, it will keep being tracked.

Editting a commit: git commit --amend [[-m <message>] [--no-edit]]

This command is extremely useful because it allows you to change last commit info such as the message or even adding or removing files. But be aware! If your commit has already been pushed to remote repo, you have to force-push it. This will come later…

If you noticed in our commit 13ab (hash), we added a message “.gitignored added”, but we want to change this message because the real name of the file is .gitignore. We can do it as follows:


$ git commit --amend

Your editor will open and you can change the message to “.gitignore added”, save it and close.


[master 85c2310] .gitignore added
    1 file changed, 1 insertion(+)
    create mode 100644 .gitignore

You also can edit it inline using git commit --amend -m <message>.


$ git commit --amend -m ".gitignore added"
[master 1d5a33b] .gitignore added
    1 file changed, 1 insertion(+)
    create mode 100644 .gitignore

If something needed to be changed but you don’t want to change the commit message, you can do it using git commit --amend --no-edit.

Showing details of a commit: git show <commit>

This command shows the details of a commit, like which files were added, removed, modified and what was modified on them. In our case, We created .gitignore file with the text “thisFileWillBeIgnored.txt”.


$ git show 85c2
commit 85c23104b895497bf00bf59e964c48e152729150
Author: Leonardo
<your@email.com>
Date: Mon Jan 26 00:55:57 2015 +0000
.gitignore added
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..79591b7
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+thisFileWillBeIgnored.txt

Viewing only the files that were changed in the last commit: git show --pretty="format:" --name-only <commit>


$ git show --pretty="format:" --name-only c158503
README

Status of a repository: git status

If you want to see the current status of the current branch of your project, you can use git status to show that like listing which files are staged, unstaged, and untracked. git status lets you inspect the working directory and the staging area.


$ git status
On branch master
Untracked files:
    (use "git add ..." to include in what will be committed)
    new_file2.txt
    nothing added to commit but untracked files present (use "git add" to track)

Logging: git log

This command displays committed snapshots and all their information. With it you can list the project history, filter it, and search for specific changes. In contrast to git status, git log only operates on the committed history.


$ git log
commit 85c23104b895497bf00bf59e964c48e152729150
Author: Leonardo
<your@email.com>
Date:   Mon Jan 26 00:55:57 2015 +0000
    .gitignore added
commit 13abdd57ba00fd53a4bf5dfeb054a2277eff5026
Author: Your Name
<your@email.com>
Date:   Fri Jan 23 13:36:05 2015 +0000
    Initial commit

Showing changed files, just add  --stat:


$ git log --stat
commit 85c23104b895497bf00bf59e964c48e152729150
Author: Leonardo
<your@email.com>
Date:   Mon Jan 26 00:55:57 2015 +0000
    .gitignore added
    .gitignore | 1 +
    1 file changed, 1 insertion(+)
commit 13abdd57ba00fd53a4bf5dfeb054a2277eff5026
Author: Your Name
<your@email.com>
Date:   Fri Jan 23 13:36:05 2015 +0000
    Initial commit
    new_file.txt | 1 +
    1 file changed, 1 insertion(+)

To shorten the messages excluding the empty lines, you can use git log --stat --oneline:


$ git log --stat --oneline
85c2310 .gitignore added
    .gitignore | 1 +
    1 file changed, 1 insertion(+)
13abdd5 Initial commit
    new_file.txt | 1 +
    1 file changed, 1 insertion(+)

Show messages formatted, just use --pretty=oneline. It also works for git show.


$ git log --pretty=oneline
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit

If you want to format a commit to a .patch file like to attach to an email, just use it: git format-patch -1 <commit>


$ git format-patch -1 85c2
0001-.gitignore-added.patch

Showing who committed the staged file: git blame <file>

Git lets you show who manipulated a file by using git blame command.


$ git blame new_file.txt
13abdd5 (Your Name 2015-01-23 13:36:05 +0000 1) First file

Showing author’s email instead the author’s name:


$ git blame -e new_file.txt
76a33985 (<your@email.com> 2015-01-26 01:27:05 +0000 1) Second file

To show the changes in a subset of commits using hashes:


$ git blame 76a3..13ab new_file.txt
13abdd5 (Leonardo Cardoso 2015-01-23 13:36:05 +0000 1) First file

If the file is big, you can use regular expressions to know who included some block of code in it.


$ git blame newest_file.txt
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  1)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  2)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  3) foo (){
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  4)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  5) }
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  6)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  7) bar (){
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  8)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000  9) }
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000 10)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000 11) main (){
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000 12)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000 13) }
$ git blame -L/^main/,/^}/ newest_file.txt
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000 11) main (){
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000 12)
40bcf0d2 (Leonardo 2015-01-26 01:32:50 +0000 13) }

Note: git blame only works on staged files.


$ git blame thisFileWillBeIgnored.txt
fatal: no such path 'thisFileWillBeIgnored.txt' in HEAD

List branch files: git ls-files

If you are a Unix-based SO user you certainly are familiar to ls command. To list the files of the current branch, use the following command:


$ git ls-files
.gitignore
new_file.txt
newest_file.txt

Viewing differences between two commits in a file: git diff

git diff shows changes between commits, commit and working tree, etc.


$ git diff
diff --git a/README b/README
index aad5bd..fd9e415 100644
--- a/README
+++ b/README
@@ -1 +1,2 @@
This is the README file.
+One more line.

git diff HEAD shows the differences between the working directory and the most recent commit:


$ git diff HEAD
diff --git a/README b/README
index aad5bd..fd9e415 100644
--- a/README
+++ b/README
@@ -1 +1,2 @@
This is the README file.
+One more line.

If you added the files, but still want to view the difference to the last commit, git diff --cached lets you see that. It shows difference between the staging area (index) and the last commit:


$ git diff --cached
diff --git a/README b/README
index aad5bd..fd9e415 100644
--- a/README
+++ b/README
@@ -1 +1,2 @@
This is the README file.
+One more line.

Viewing differences between two commits in a file: git diff <hash>..<hash> <file>


$ git diff 76a3..13ab new_file.txt
diff --git a/new_file.txt b/new_file.txt
index 20d5b67..4c5fd91 100644
--- a/new_file.txt
+++ b/new_file.txt
@@ -1 +1 @@
-Second file
+First file

Creating branches: git branch

One of the most important things on Git is branches. When you create a new branch, it will have the same history and files of the source branch which you created a new one from, unless you specify the commit. To create a new branch, just type: git branch <branch>.


$ git branch developer

To list branches, just use: git branch. The * indicates the current branch your project is at.


$ git branch
developer
* master

To list all branches, local and remote, just use: git branch -a.


$ git branch -a
developer
* master
remotes/origin/developer
remotes/origin/master

To go to the new branch, just use: git checkout <branch>


$ git checkout developer
Switched to branch ‘'developer'

To create a new branch from specified commit, just use: git checkout <branch> <commit>.


$ git branch new_branch_name 0aa034c

Delete a branch: git branch -d <branch>

Deleting a branch is simple: git branch -d <branch>.


$ git branch -d developer
Deleted branch developer (was 48f97a4).

To force deletion, use a capital “D”: git branch -D <branch>.

Note: A branch can only be deleted if the project is not currently checked out at that branch.

Adding a remote repo: git remote

This command lets you create, view, and delete connections to other repositories. It’s mostly used to add the bare repository of your local repository. git remote add origin <path>.


$ git remote add origin ../git_init_bare
$ git remote add origin https://github.com/LeonardoCardoso/Movement.git

To change the origin path of repo with an origin already, you can use the following command: git remote set-url origin <path>.


$ git remote set-url origin ../git_101_bare

To check out the origin, just use:


$ git remote -v
    origin ../git_101_bare (fetch)
    origin ../git_101_bare (push)

Pushing to a repo: git push <remote> <branch>

Pushing to a repo means to send all your local committed modifications to the remote branch that you specify. It can be done by the following command: git push <remote> <branch>.


$ git push origin master
Counting objects: 12, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (7/7), done.
Writing objects: 100% (12/12), 1010 bytes | 0 bytes/s, done.
Total 12 (delta 1), reused 0 (delta 0)
To ../git_101_bare/
    * [new branch]      master -> master

You can also force a push by using one of the two commands: git push <remote> <branch> --force or git push -f <remote> <branch>


$ git push origin master -f

Warning: force-pushing will overwrite the remote branch with the state of your local one. If there are commits on remote branch that you don’t have in your local branch, you will lose those commits. Warning: be cautious about amending commits that you have already shared with other people. Amending commits essentially rewrites them. So they will have different hashes, which creates a problem if other people have copies of the old commit that you’ve rewritten. Anyone who has a copy of the old commit will need to re-synchronize their work with your newly re-written commit, which can sometimes be difficult. So although the usefulness of amending, avoid to do that if you shared the previous one with other developers.

Fetching a branch: git fetch <remote> [<remote branch>] [:<local branch>]

This command imports commits from a remote repository into your local repo. The resulting commits are stored as remote branches instead of the normal local branches. To fetch all branches from the origin repo. git fetch <remote>.


$ git fetch origin

Same as the above command, but only fetch the specified branch: git fetch <remote> <remote branch>.


$ git fetch origin developer

If you want to fetch a branch and automatically create a local branch linked to it, use: git fetch <remote> <remote branch>:<local branch>


$ git fetch origin developer:dev
From ../git_101_bare
    * branch developer  -> FETCH_HEAD

Our last example will create a local branch named dev that links to developer. If you do not add the local branch on git command (:), the branch will be fetched to your local repo as a remote branch, but no working copy branch will be created to link that.

Pulling a branch: git pull  

git pull does a git fetch followed by a git merge. As told before, you can use git fetch whenever you want to update your remote-tracking branches under refs/remotes/<remote>. It won’t affect your working copy though.

However, if there is an update on a remote branch and your working copy branch is not up to date with the new modifications, but you want to bring the updates and automatically merge it, you can simply use: git pull <remote> <branch>.


$ git pull origin developer
From ../git_101_bare
* branch developer -> FETCH_HEAD
Already up-to-date.

Merging branches: git merge 

git merge is design to join two or more development histories together. To merge them, you can use: git merge <branch>.


$ git checkout master
$ git merge developer
Updating 40bcf0d..9e97315
Fast-forward
    file_on_dev_branch.txt | 0
    1 file changed, 0 insertions(+), 0 deletions(-)
    create mode 100644 file_on_dev_branch.txt

The file we created on developer branch is brought to master branch.

Manipulating Multiple Commits: git rebase

This command allows you to edit multiple commits messages or join commits. The command is git rebase -i <commit>. But instead of using the commit hash, you can use HEAD~<number of commits> that will show the previous N commits before the most recent one. For example: $ git rebase -i HEAD~3


$ git rebase -i 9e97
pick 40bcf0d newest_file.txt added
pick 9e97315 Filed added on Dev branch
pick 18b2e67 File on third branch
# Rebase 76a3398..18b2e67 onto 76a3398
#
# Commands:
#  p, pick = use commit
#  r, reword = use commit, but edit the commit message
#  e, edit = use commit, but stop for amending
#  s, squash = use commit, but meld into previous commit
#  f, fixup = like "squash", but discard this commit's log message
#  x, exec = run command (the rest of the line) using shell
#
# 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

When you use this command, the commit you chose is selected and all of the commits before that one are listed.

For example, we want to change the commit message of 9e97315. So we only need to change the word pick at left side of 9e97315 to reword and save the file.

After that, you file editor will open to change the message.


reword 9e97315 Filed added on Dev branch
A new file added on Developer branch
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# rebase in progress; onto 76a3398
# You are currently editing a commit while rebasing branch 'third' on '76a3398'.
#
# Changes to be committed:
#     new file:   file_on_dev_branch.txt
#
[detached HEAD b0c6af7] A new file added on Developer branch
    1 file changed, 0 insertions(+), 0 deletions(-)
    create mode 100644 file_on_dev_branch.txt
Successfully rebased and updated refs/heads/developer.

To check, let’s go to the log.


$ git log --pretty=oneline
0648d95242ff6ea5705b344aa0c86f6d956d8888 One more file on dev
b0c6af74e252828ae8b44791f5787b9f78ce3b6a A new file added on Developer branch
40bcf0d2c74384cd6d0514883718ab25c162cd14 newest_file.txt added
76a339851ee01b5eedd9d787d232b4cc5da595cc Changed content new_file.txt
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit

To join commits, you use squash. The commit you will squashed will be combined to the previous commit.


pick 85c2310 .gitignore added
pick 76a3398 Changed content new_file.txt
squash 40bcf0d newest_file.txt added
pick b0c6af7 A new file added on Developer branch
pick 0648d95 One more file on dev
# Rebase 13abdd5..0648d95 onto 13abdd5

When you save the file, the file editor will be prompted.


# This is a combination of 2 commits.
# The first commit's message is:
Changed content new_file.txt
# This is the 2nd commit message:
newest_file.txt added
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# rebase in progress; onto 13abdd5
# You are currently editing a commit while rebasing branch 'developer' on '13abdd5'.
#
# Changes to be committed:
#     modified:   new_file.txt
#     new file:   newest_file.txt
#

Here we removed those two commit messages and we put the message “Squashed commit” instead and save it.


Squashed commit
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# rebase in progress; onto 13abdd5
# You are currently editing a commit while rebasing branch 'developer' on '13abdd5'.
#
# Changes to be committed:
#     modified:   new_file.txt
#     new file:   newest_file.txt
#
$ git log --pretty=oneline
2ff5a4e099b7798787fe8e00167211c1e3e2afe2 One more file on dev
e6b0e3a59acf76cd41f53752178d6de9768a9247 A new file added on Developer branch
da7176b55efd62e999a2a82e7f254d37498034c0 Squashed commit
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit

Revert to a previous Git commit: git revert

This command undoes a committed snapshot. But instead of removing the commit from the project history, it undoes the changes introduced by the commit and appends a new commit. This prevents Git from losing history, which is important for the integrity.


$ git log --pretty=oneline
dd0562dfca2fecf5c938857689a24a40fcb304ae Merge branch 'developer' of ../git_101_bare into developer
2ff5a4e099b7798787fe8e00167211c1e3e2afe2 One more file on dev
e6b0e3a59acf76cd41f53752178d6de9768a9247 A new file added on Developer branch
da7176b55efd62e999a2a82e7f254d37498034c0 Squashed commit
18b2e6771a04dc2ceabf9c4b2dcb4a00d9815eb5 File on third branch
9e97315bcbc29140db0a6d8245c5c7a69143cdda Filed added on Dev branch
40bcf0d2c74384cd6d0514883718ab25c162cd14 newest_file.txt added
76a339851ee01b5eedd9d787d232b4cc5da595cc Changed content new_file.txt
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit
$ git revert 18b2
[developer 0494017] Revert "File on third branch"
    1 file changed, 0 insertions(+), 0 deletions(-)
    delete mode 100644 file.txt
$ git log --pretty=oneline
04940178e51e297cd577eab608a417850c430949 Revert "File on third branch"
dd0562dfca2fecf5c938857689a24a40fcb304ae Merge branch 'developer' of ../git_101_bare into developer
2ff5a4e099b7798787fe8e00167211c1e3e2afe2 One more file on dev
e6b0e3a59acf76cd41f53752178d6de9768a9247 A new file added on Developer branch
da7176b55efd62e999a2a82e7f254d37498034c0 Squashed commit
18b2e6771a04dc2ceabf9c4b2dcb4a00d9815eb5 File on third branch
9e97315bcbc29140db0a6d8245c5c7a69143cdda Filed added on Dev branch
40bcf0d2c74384cd6d0514883718ab25c162cd14 newest_file.txt added
76a339851ee01b5eedd9d787d232b4cc5da595cc Changed content new_file.txt
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit

Revert to a previous Git commit: git checkout

This command allows to checkout a branch (showed previously), paths to the working tree or take the branch to some commit in history: git checkout <commit>.


$ git log --pretty=oneline
2ff5a4e099b7798787fe8e00167211c1e3e2afe2 One more file on dev
e6b0e3a59acf76cd41f53752178d6de9768a9247 A new file added on Developer branch
da7176b55efd62e999a2a82e7f254d37498034c0 Squashed commit
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit
$ git checkout e6b0
HEAD is now at e6b0e3a... A new file added on Developer branch
$ git log --pretty=oneline
e6b0e3a59acf76cd41f53752178d6de9768a9247 A new file added on Developer branch
da7176b55efd62e999a2a82e7f254d37498034c0 Squashed commit
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit

Undoing accidental deletions.


$ git checkout -f

Force Git to overwrite local files: git reset

If you want to throw out all of the changes you’ve been working on, you can use: $ git reset - HARD [<commit>].

If you don’t insert the commit, it will be reseted to the most recent commit on remote.


$ git reset --HARD 18b2
HEAD is now at 18b2e67 File on third branch
$ git log --pretty=oneline
18b2e6771a04dc2ceabf9c4b2dcb4a00d9815eb5 File on third branch
9e97315bcbc29140db0a6d8245c5c7a69143cdda Filed added on Dev branch
40bcf0d2c74384cd6d0514883718ab25c162cd14 newest_file.txt added
76a339851ee01b5eedd9d787d232b4cc5da595cc Changed content new_file.txt
85c23104b895497bf00bf59e964c48e152729150 .gitignore added
13abdd57ba00fd53a4bf5dfeb054a2277eff5026 Initial commit

Stashing modifications: git stash

Stashing is a great way to pause what you’re currently working on and come back to it later. Say that we are making some changes and we are not done yet, but someone needs urgently that we fix some thing in some previous commit. So we can freeze our local modifications using: git stash.


$ git add .
$ git stash
Saved working directory and index state WIP on developer: 8178777 Merge branch 'developer'
HEAD is now at 8178777 Merge branch 'developer'

So,the files go back to state on the most recent commit on tracking. After we do the fixes, we just need to use git stash list to visualize the existing stashes.


$ git stash list
stash@{0}: WIP on (no branch): 2ff5a4e One more file on dev

And to apply the stash we use git stash apply stash@<stash number>.


$ git stash apply stash@{0}
On branch developer
Changes not staged for commit:
(use "git add
..." to update what will be committed)
(use "git checkout --
..." to discard changes in working directory)
modified:   one_more_file_on_dev.txt
no changes added to commit (use "git add" and/or "git commit -a")

We can quickly apply the last stash using git stash pop. With this command, the applied stash is also deleted.

Cleaning up untracked files: git clean

Files may pile up in your working directory that are left over from merges, generated, or even put mistakenly there. No matter what, you don’t need to ignore them in .gitignore, you just need to remove them. This command dries up the current branch. The following command will list the files to be removed: git clean -n -d <path>.


$ git clean -n -d -x
Would remove .DS_Store
Would remove thisFileWillBeIgnored.txt

The command to clean is git clean -i -d -x.


$ git clean -i -d -x
Would remove the following items:
    .DS_Store                  thisFileWillBeIgnored.txt
*** Commands ***
    1: clean                2: filter by pattern    3: select by numbers    4: ask each
    5: quit                 6: help
What now> 1
Removing .DS_Store
Removing thisFileWillBeIgnored.txt

Bringing specific commit to current branch: git cherry-pick

Cherry-picking 🍒 in git means to choose a commit from one branch and apply it onto another. So there is no need to merge the entire branch. Make sure you are in the right branch to cherry-pick the commit from another. To do that, use git cherry-pick <commit-hash>.


$ git cherry-pick 45fd
Finished one cherry-pick.
[master]: created 567ed1: “README file."
1 file changed, 1 insertions(+), 0 deletions(-)
create mode 100644 README.txt

Tagging releases: git tag

Tags are used to freeze stable releases. To do that, simply use the following code: git tag <version>.


$ git tag 1.0
$ git push --tags
Counting objects: 7, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 417 bytes | 0 bytes/s, done.
Total 3 (delta 1), reused 0 (delta 0)
To ../git_101_bare/
    * [new tag]         1.0 -> 1.0
$ git tag 2.0
$ git push origin tag 2.0
Total 0 (delta 0), reused 0 (delta 0)
To ../git_101_bare/
    * [new tag]         2.0 -> 2.0

Listing tags:


$ git tag -l
1.0
2.0

Logging the whole thing: git reflog

Reflog is a mechanism on which Git tracks the updates to the tip of branches. Even though the changesets are not referenced by any branch or tag. Thus you can go back to them. After rewriting history, the reflog contains information about the old state of branches.


$ git reflog
18b2e67 HEAD@{0}: checkout: moving from developer to third
48f97a4 HEAD@{1}: checkout: moving from master to developer
8178777 HEAD@{2}: checkout: moving from third to master
18b2e67 HEAD@{3}: checkout: moving from master to third
8178777 HEAD@{4}: merge developer: Merge made by the 'recursive' strategy.
18b2e67 HEAD@{5}: merge third: Fast-forward
9e97315 HEAD@{6}: checkout: moving from developer to master
48f97a4 HEAD@{7}: commit: One more file on dev
9e97315 HEAD@{8}: checkout: moving from master to developer
9e97315 HEAD@{9}: checkout: moving from third to master
18b2e67 HEAD@{10}: commit: File on third branch
9e97315 HEAD@{11}: checkout: moving from master to third
9e97315 HEAD@{12}: merge developer: Fast-forward
40bcf0d HEAD@{13}: checkout: moving from developer to master
9e97315 HEAD@{14}: commit: Filed added on Dev branch
40bcf0d HEAD@{15}: checkout: moving from master to developer
40bcf0d HEAD@{16}: commit: newest_file.txt added
76a3398 HEAD@{17}: commit: Changed content new_file.txt
85c2310 HEAD@{18}: commit (amend): .gitignore added
44e0174 HEAD@{19}: commit: .gitignored added
13abdd5 HEAD@{20}: commit (initial): Initial commit

To go back to an old state, use git reset --hard <commit hash>.

Resolving conflicts

In many cases, you might see conflicts. They basically consist of the same part of a file is changed on commits in two different branches without being updated before (merging).

For example, if you make a change on a particular line in a file and your colleague working in a repository makes a change on the exact same line, a merge conflict occurs. To solve that, you need to merge the file checking which differences must be remained in the file. And then after resolving the conflicts, you can add the file to index back again.

A conflict-marked area begins with <<<<<<< and ends with >>>>>>>, they are called conflict markers. The two conflicting blocks themselves are divided by a =======. They need to be removed from the file after you inspect the file.


<<<<<<< HEAD
Here is the original change.
=======
Here is the modified change.
>>>>>>> 99db324742823c55d975b605e1fc22f4253a9b7d

On this post, there are the main commands that you will use. But there are many others that you can check it out on its official documentation.

Pull Requests: You Better Use Them »