Basic Git Commands

Concepts

• Think of git system like a warehouse. There are three places each file can be: being outside the warehouse (“untracked”), being in the warehouse but still in loading zone (“staged”), being organized and put on shelves (“committed”). (Well, that is just my understanding…).

Basic configuration

• One must to set the username and password before being able to commit. One can do it system-wide like

git config --global user.name "John Doe"
git config --global user.email [email protected]

or only set this information locally to a specific repository

git config user.name "John Doe"
git config user.email [email protected]

If same records exist in both global and local settings, local ones are prioritized.

• Set the editor for editting the commit message:

git config --global core.editor "vim"

or set “export GIT_EDITOR=vim” in “~/.bashrc/”.

Staging and committing

• Check file status

git status

• Add untracked files to stage, or update tracked but modified files to stage

git add [files]

A short-hand

git add . 

will stage all files under current directory

• Commit

git commit -m 'commit message'

or just

git commit

followed by inputing the commit message interactively.

• Another short-hand skipping git add:

git commit -a -m 'commit message'

• Move file

git mv file_from file_to

Viewing changes

• View what is changed but still not stage

git diff 

• View what is staged that will go to the next commit

git diff --cached

or

git diff --staged

Viewing git log

• Most general command

git log

• Show the difference introduced in last 2 commits

git log -p -2

• Show abbreviated diff stats

git log --stat

• The --pretty flag formats the git log output. For example, to format the git log output in form of one line for each commit

git log --pretty=oneline

• Show branching and merging history in ASCII-art like style using --graph flag

git log --pretty=format:"%h, %s" --graph

The meaning of %h and %s can be found below:

Option  Description of Output
%H  Commit hash
%h  Abbreviated commit hash
%T  Tree hash
%t  Abbreviated tree hash
%P  Parent hashes
%p  Abbreviated parent hashes
%an Author name
%ae Author e-mail
%ad Author date (format respects the –date= option)
%ar Author date, relative
%cn Committer name
%ce Committer email
%cd Committer date
%cr Committer date, relative
%s  Subject

• Show commit log in last two weeks

git log --since=2.weeks

and some useful option flags:

Option  Description
-(n)    Show only the last n commits
--since, --after    Limit the commits to those made after the specified date.
--until, --before   Limit the commits to those made before the specified date.
--author    Only show commits in which the author entry matches the specified string.
--committer Only show commits in which the committer entry matches the specified string.

• Show tree structure with “git log” command

git log --graph --decorate --all

• A GUI tool to view the git log is

gitk

Undoing things

• Change the last commit, such as adding a forgotten file, editing the commit message, etc.

git commit --amend

That is convenient: it allows you to commit frequency, and in the end it can just be commit if using this amend command after each commit. An example will be

git commit -a -m 'update'
git add forgotten_file
git commit --amend -m 'update2'
git add another_forgotten_file
git commit --amend 'update3'

And in the end there will just be one commit in the log with commit message “update3”.

• Change author in an amended commit

git commit --amend --reset-author 'update4'

• Revert a ‘git add’ before ‘git commit’, that is, unstage files that are already staged:

git reset HEAD [files]

which will leave the file as “modified”. To even discard the changes made since last commit, that is, unmodify modified files:

git checkout -- [files]

But “git checkout” will not remove the untracked files and directories. Use “git clean” to remove the untracked ones, do

git clean -f    # remove untracked files
git clean -df   # remove untracked directories

See the documentation for “git-clean” for details.

Rolling back to previous commits

First check out a commit from the history:

git checkout [commit] . 

Note that the period “.” in the end means apply the changes to the current stage.

If only need to check out a specific file of a specific commit, do:

git checkout [commit] [file-path]

And then commit the changes and make a new commit:

git add . 
git commit -m "message"

Removing and moving files

• Remove files both from git stage and physical hard drive

git rm [files]

• Remove files only from git stage, but still keep it on physical hard drive

git rm --cached [files]

which will leave files as “untracked”.

Working with remotes

• Show remotes

git remote

• Add a remote

git remote add [remote_nickname] [remote_url]

such as

git remote add origin [email protected]:vadiode/git_notes.git

• Show information about a remote

git remote show [remote_nickname]

or with flag -v

git remote show [remote_nickname] -v

• Rename a remote

git remote rename [old_remote_name] [new_remote_name]

Edit the remote url

git remote set-url origin new_url

Git remote with a custom SSH port (other than 22): edit ~/.ssh/config like this

Host example.com
Port 1234

• Remove a remote

git remote rm [remote_name]

• Push a local branch to remote branch

git push [remote_name] [local_branch_name]:[remote_branch_name]

If the local branch and remote branch have the same names, this command can be shortened as:

git push [remote_name] [branch_name]

Tagging

• Tags can be either lightweight (just a tag name), or annotated (with tagging message). If it is annotated, it can be even signed with GPG.

• A newly created tag will not be pushed to remote by default. A git push is needed if you want to do that.

• Show existing tags

git tag

• Show existing tags with a pattern (using wildcards)

git tag -l 'v1.4.*'

• Show tag information

git show [tag_name]

such as

git show v1.4.0

• Apply a lightweight tag (with no tagging message) to the current commit

git tag v1.4.1-lw

• Apply an annotated tag to the current commit

git tag -a v1.4.1 -m 'version 1.4.1, finished in 12/11/2011'

• Sign a tag with GPG, using -s flag

git tag -s -a v1.4.1 -m 'version 1.4.1, finished in 12/11/2011, with signature'

• Tag a specific commit

git tag -a [tag_name] [commit_hash]

such as

git tag -a v1.4.1 9fceb02

• Push a tag to remote

git push [remote_name] [tag_name]

such as

git push origin v1.4.1

• Push all tags to remote

git push origin --tags

Useful Git Commands

• Compare changed files between two commits. See this post.

git diff --name-only SHA1 SHA2

Omitting “–name-only” flag will make it show the diff of file content.