Basic Git Commands

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Contents

Git commands can be searched everywheere. Here I will list only the commonly used ones in my development.

First of all, try the following commands first:

Branch Operation

To checkout a new branch from remote repo: When you want to change to a branch that is not in your local side, use git branch -a to list all the branches, and find the one you want to checkout in the remote. Then run git checkout --track origin/<branch_name>, and you will get the branch. Use git branch to check it.

Check commit history

First, use git log to find the commit we want. We can use git log –author=someone to narrow the scope.

Then, use git diff COMMIT^ COMMIT to get all the changes of one commit.

.gitignore

Sometimes we want to ignore some files/folders from being tracked by git. We can use .gitignore file to do this. But this only works for the untracked items. If you have done git add file to the file once, .gitignore will not exclude this file from being tracked. For this case, we can use the following two ways to ignore the file:

git rm \-\-cached file

This command will remove the file from the stage, and if you exclude the file in the .gitignore, it will not appear in the untrancked files list. But you will get a deleted: file in the changes to be commited list, and the next time you commit, the file in the repo will be deleted.

If this is not what you want, and you only want to ignore the file locally, and don’t want to remove it in the repo, because someone else may need this file, go to the second method.

git update-index \-\-assume-unchanged file

This method doesn’t need .gitignore, and will not delete the file in the repo. The disadvantage is: when you clone the repo in other places, you need to run the command again.

Using git stash

Reference:

Description

When you are woring on a newbranch which is based on an oldbranch, and have some uncommitted changes in newbranch. But now your manager notice you that there is an urgent issue needs to be fixed in the oldbranch right now, and you don’t want to commit your changes in newbranch, what should we do here?

Solution

When we trying to checkout oldbranch using git checkout oldbranch, what is git doing? There may be three ways:

  1. Ignore the uncommitted working directory changes in newbranch, and set the working directory to the files in the oldbranch. The uncommited changes in the newbranch will be lost.
  2. Ignore the state of the files in oldbranch, and use the working directory files in newbranch. Completely wrong! This will not confirm with the original oldbranch.
  3. Attempt to merge in the changes from the working directory in newbranch into the files in oldbranch.

Git actually tries to use #3 method.

With no confilicts

checkout oldbranch from newbranch with uncommitted changes in newbranch, but NO Conflicts between the two branches

The sample log:

1 M	test.txt
2 Switched to branch 'oldbranch'

And the M means the test.txt is successfully merged.

With Conflicts

checkout oldbranch from newbranch with uncommitted changes in newbranch, but With Conflict between the two branches. In this situation, if you want to checkout oldbranch any way, use git checkout -m oldbranch which will let git list all the conflicts, as follows:

 1 $ git checkout -m oldbranch
 2 M   test.txt
 3 Switched to branch 'oldbranch'
 4 $ cat test.txt
 5 This is the test file.
 6 <<<<<<< oldbranch
 7 Second line added from the 'oldbranch' branch.
 8 =======
 9 A conflicted line added on the test branch.
10 >>>>>>> local
11 $ git branch
12 * oldbranch
13   newbranch
git stash

But most of the time, we want to keep the uncommited changes staying in newbranch, and oldbranch as it was. And when we finish the work in oldbranch and get back to newbranch, the uncommited changes is still there. For this purpose, we need git stash:

  1. in newbranch, run git stash. Check git status, and there will be nothing changed.
  2. git checkout oldbranch.
  3. Work in oldbranch, and commit the changes.
  4. git checkout newbranch
  5. git stash pop

Git will hold a stash stack for all the stashes in all branches. That is to say, no matter how many branches you have, you will have only one stash stack. So when you run git stash pop, you should check the stash stack using git stash list, you will get:

1 stash@{0}: WIP on oldbranch: 6ed44e2 checkin a new file
2 stash@{1}: WIP on newbranch: 7a51723 checkin
3 stash@{2}: WIP on oldbranch: 022cbf7 first checkin
4 stash@{3}: WIP on newbranch: 6995c80 checkin changes to test.txt

If you want to roll back the last stash in newbranch, in #5 step, run git stash pop stash@{1}. If you don’t use the index stash@{1}, the top stash in the stash stack will be popped out.

Use kdiff3 as the default tool for git

When you run git diff, the difference will be listed in the command window. If you want to see the difference in a visual window (for exmple, kdiff3):

  1. install kdiff3 in your mac

  2. As the new version of git has build-in support for kdiff3, so there is no need for manually configuration, just run 

     $ git config --global merge.tool *kdiff3*

  3. If kdiff3 is not in your path, run 

     $ git config --global mergetool.kdiff3.path /Applications/kdiff3.app/Contents/MacOS/kdiff3
  4. Use git difftool instead of git diff to let git launch kdiff3 for the difference. Also use git mergetool instead of git merge for merging files.