git command
create a new repository
create a new directory, open it and perform a
git init
to create a new git repository.
checkout a repository
create a working copy of a local repository by running the command
git clone /path/to/repository
when using a remote server, your command will be
git clone username@host:/path/to/repository
workflow
your local repository consists of three "trees" maintained by git. the first one is your Working Directory which holds the actual files. the second one is the Index which acts as a staging area and finally the HEAD which points to the last commit you've made.
add & commit
You can propose changes (add it to the Index) using
git add <filename>
git add *
This is the first step in the basic git workflow. To actually commit these changes use
git commit -m "Commit message"
Now the file is committed to the HEAD, but not in your remote repository yet.
pushing changes
Your changes are now in the HEAD of your local working copy. To send those changes to your remote repository, execute
git push origin master
Change master to whatever branch you want to push your changes to.
If you have not cloned an existing repository and want to connect your repository to a remote server, you need to add it with
git remote add origin <server>
Now you are able to push your changes to the selected remote server
branching
Branches are used to develop features isolated from each other. The master branch is the "default" branch when you create a repository. Use other branches for development and merge them back to the master branch upon completion.
create a new branch named "feature_x" and switch to it using
git checkout -b feature_x
switch back to master
git checkout master
and delete the branch again
git branch -d feature_x
a branch is not available to others unless you push the branch to your remote repository
git push origin <branch>
update & merge
to update your local repository to the newest commit, execute
git pull
in your working directory to fetch and merge remote changes.
to merge another branch into your active branch (e.g. master), use
git merge <branch>
in both cases git tries to auto-merge changes. Unfortunately, this is not always possible and results in conflicts. You are responsible to merge those conflicts manually by editing the files shown by git. After changing, you need to mark them as merged with
git add <filename>
before merging changes, you can also preview them by using
git diff <source_branch> <target_branch>
tagging
it's recommended to create tags for software releases. this is a known concept, which also exists in SVN. You can create a new tag named 1.0.0 by executing
git tag 1.0.0 1b2e1d63ff
the 1b2e1d63ff stands for the first 10 characters of the commit id you want to reference with your tag. You can get the commit id by looking at the...
log
in its simplest form, you can study repository history using.. git log
You can add a lot of parameters to make the log look like what you want. To see only the commits of a certain author:
git log --author=bob
To see a very compressed log where each commit is one line:
git log --pretty=oneline
Or maybe you want to see an ASCII art tree of all the branches, decorated with the names of tags and branches:
git log --graph --oneline --decorate --all
See only which files have changed:
git log --name-status
These are just a few of the possible parameters you can use. For more, see git log --help
replace local changes
In case you did something wrong, which for sure never happens ;), you can replace local changes using the command
git checkout -- <filename>
this replaces the changes in your working tree with the last content in HEAD. Changes already added to the index, as well as new files, will be kept.
If you instead want to drop all your local changes and commits, fetch the latest history from the server and point your local master branch at it like this
git fetch origin
git reset --hard origin/master
useful hints
built-in git GUI
gitk
use colorful git output
git config color.ui true
show log on just one line per commit
git config format.pretty oneline
use interactive adding
git add -i
links & resources
graphical clients
guides
get help
Modify Existing Function
Tom performs the clone operation and finds a new file string.c. He wants to know who added this file to the repository and for what purpose, so, he executes the git log command.
[tom@CentOS ~]$ git clone gituser@git.server.com:project.git
The above command will produce the following result:
Initialized empty Git repository in /home/tom/project/.git/ remote: Counting objects: 6, done. remote: Compressing objects: 100% (4/4), done. Receiving objects: 100% (6/6), 726 bytes, done. remote: Total 6 (delta 0), reused 0 (delta 0)
The Clone operation will create a new directory inside the current working directory. He changes the directory to newly created directory and executes the git log command.
[tom@CentOS ~]$ cd project/ [tom@CentOS project]$ git log
The above command will produce the following result:
commit d1e19d316224cddc437e3ed34ec3c931ad803958 Author: Jerry Mouse <jerry@tutorialspoint.com> Date: Wed Sep 11 08:05:26 2013 +0530 Changed return type of my_strlen to size_t commit 19ae20683fc460db7d127cf201a1429523b0e319 Author: Tom Cat <tom@tutorialspoint.com> Date: Wed Sep 11 07:32:56 2013 +0530 Initial commit
After observing the log, he realizes that the file string.c was added by Jerry to implement basic string operations. He is curious about Jerry’s code. So he opens string.c in text editor and immediately finds a bug. In my_strlen function, Jerry is not using a constant pointer. So, he decides to modify Jerry’s code. After modification, the code looks as follows:
[tom@CentOS project]$ git diff
The above command will produce the following result:
diff --git a/string.c b/string.c index 7da2992..32489eb 100644 --- a/string.c +++ b/string.c @@ -1,8 +1,8 @@ #include <stdio.h> -size_t my_strlen(char *s) +size_t my_strlen(const char *s) { - char *p = s; + const char *p = s; while (*p) ++p; }
After testing, he commits his change.
[tom@CentOS project]$ git status -s M string.c ?? string [tom@CentOS project]$ git add string.c [tom@CentOS project]$ git commit -m 'Changed char pointer to const char pointer' [master cea2c00] Changed char pointer to const char pointer 1 files changed, 2 insertions(+), 2 deletions(-) [tom@CentOS project]$ git log
The above command will produce the following result:
commit cea2c000f53ba99508c5959e3e12fff493b Author: Tom Cat <tom@tutorialspoint.com> Date: Wed Sep 11 08:32:07 2013 +0530 Changed char pointer to const char pointer commit d1e19d316224cddc437e3ed34ec3c931ad803958 Author: Jerry Mouse <jerry@tutorialspoint.com> Date: Wed Sep 11 08:05:26 2013 +0530 Changed return type of my_strlen to size_t commit 19ae20683fc460db7d127cf201a1429523b0e319 Author: Tom Cat <tom@tutorialspoint.com> Date: Wed Sep 11 07:32:56 2013 +0530 Initial commit
Tom uses git push command to push his changes.
[tom@CentOS project]$ git push origin master
The above command will produce the following result:
Counting objects: 5, done. Compressing objects: 100% (3/3), done. Writing objects: 100% (3/3), 336 bytes, done. Total 3 (delta 1), reused 0 (delta 0) To gituser@git.server.com:project.git d1e19d3..cea2c00 master −> master
Add New Function
Meanwhile, Jerry decides to implement string compare functionality. So he modifies string.c. After modification, the file looks as follows:
[jerry@CentOS project]$ git diff
The above command will produce the following result:
index 7da2992..bc864ed 100644 --- a/string.c +++ b/string.c 30Git Tutorials @@ -9,9 +9,20 @@ size_t my_strlen(char *s) return (p -s ); } +char *my_strcpy(char *t, char *s) + { + char *p = t; + + while (*t++ = *s++) + ; + + return p; + } + int main(void) { int i; + char p1[32]; char *s[] = { "Git tutorials", "Tutorials Point" @@ -20,5 +31,7 @@ int main(void) for (i = 0; i < 2; ++i) printf("string lenght of %s = %lu\n", s[i], my_strlen(s[i])); + printf("%s\n", my_strcpy(p1, "Hello, World !!!")); + return 0; } }
After testing, he is ready to push his change.
[jerry@CentOS project]$ git status -s M string.c ?? string [jerry@CentOS project]$ git add string.c [jerry@CentOS project]$ git commit -m "Added my_strcpy function" [master e944e5a] Added my_strcpy function 1 files changed, 13 insertions(+), 0 deletions(-)
Before push operation, he verifies commit by viewing log messages.
[jerry@CentOS project]$ git log
The above command will produce the following result:
commit e944e5aab74b26e7447d3281b225309e4e59efcd Author: Jerry Mouse <jerry@tutorialspoint.com> Date: Wed Sep 11 08:41:42 2013 +0530 Added my_strcpy function commit d1e19d316224cddc437e3ed34ec3c931ad803958 Author: Jerry Mouse <jerry@tutorialspoint.com> Date: Wed Sep 11 08:05:26 2013 +0530 Changed return type of my_strlen to size_t commit 19ae20683fc460db7d127cf201a1429523b0e319 Author: Tom Cat <tom@tutorialspoint.com> Date: Wed Sep 11 07:32:56 2013 +0530 Initial commit
Jerry is happy with the changes and he wants to push his changes.
[jerry@CentOS project]$ git push origin master
The above command will produce the following result:
To gituser@git.server.com:project.git ! [rejected] master −> master (non-fast-forward) error: failed to push some refs to 'gituser@git.server.com:project.git' To prevent you from losing history, non-fast-forward updates were rejected Merge the remote changes before pushing again. See the 'Note about fast-forwards' section of 'git push --help' for details.
But Git is not allowing Jerry to push his changes. Because Git identified that remote repository and Jerry’s local repository are not in sync. Because of this, he can lose the history of the project. To avoid this mess, Git failed this operation. Now, Jerry has to first update the local repository and only thereafter, he can push his own changes.
Fetch Latest Changes
Jerry executes the git pull command to synchronize his local repository with the remote one.
[jerry@CentOS project]$ git pull
The above command will produce the following result:
remote: Counting objects: 5, done. remote: Compressing objects: 100% (3/3), done. remote: Total 3 (delta 1), reused 0 (delta 0) Unpacking objects: 100% (3/3), done. From git.server.com:project d1e19d3..cea2c00 master −> origin/master First, rewinding head to replay your work on top of it... Applying: Added my_strcpy function
After pull operation, Jerry checks the log messages and finds the details of Tom’s commit with commit ID cea2c000f53ba99508c5959e3e12fff493ba6f69
[jerry@CentOS project]$ git log
The above command will produce the following result:
commit e86f0621c2a3f68190bba633a9fe6c57c94f8e4f Author: Jerry Mouse <jerry@tutorialspoint.com> Date: Wed Sep 11 08:41:42 2013 +0530 Added my_strcpy function commit cea2c000f53ba99508c5959e3e12fff493ba6f69 Author: Tom Cat <tom@tutorialspoint.com> Date: Wed Sep 11 08:32:07 2013 +0530 Changed char pointer to const char pointer commit d1e19d316224cddc437e3ed34ec3c931ad803958 Author: Jerry Mouse <jerry@tutorialspoint.com> Date: Wed Sep 11 08:05:26 2013 +0530 Changed return type of my_strlen to size_t commit 19ae20683fc460db7d127cf201a1429523b0e319 Author: Tom Cat <tom@tutorialspoint.com> Date: Wed Sep 11 07:32:56 2013 +0530 Initial commit
Now, Jerry’s local repository is fully synchronized with the remote repository. So he can safely push his changes.
[jerry@CentOS project]$ git push origin master
The above command will produce the following result:
Counting objects: 5, done. Compressing objects: 100% (3/3), done. Writing objects: 100% (3/3), 455 bytes, done. Total 3 (delta 1), reused 0 (delta 0) To gituser@git.server.com:project.git cea2c00..e86f062 master −> master