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Using Git as you work

Know what branch you're working on

When using Git, it's important to know which branch you currently have checked out because most git commands implicitly operate on the current branch. You can determine the currently checked out branch several ways.

One way is with git status:

$ git status
On branch issue-demo
nothing to commit, working directory clean

Another is with git branch which will display all local branches, with a star next to the current branch:

$ git branch
* issue-demo
  master

To see even more information about your branches, including remote branches, use git branch -vva:

$ git branch -vva
* issue-123                 517468b troubleshooting tip about provisioning
  master                    f0eaee6 [origin/master] bug: Fix traceback in get_missed_message_token_from_address().
  remotes/origin/HEAD       -> origin/master
  remotes/origin/issue-1234 4aeccb7 Another test commit, with longer message.
  remotes/origin/master     f0eaee6 bug: Fix traceback in get_missed_message_token_from_address().
  remotes/upstream/master   dbeab6a Optimize checks of test database state by moving into Python.

You can also configure Bash and Zsh to display the current branch in your prompt.

Keep your fork up to date

You'll want to keep your fork up-to-date with changes from Zulip's main repositories.

Note about git pull: You might be used to using git pull on other projects. With Zulip, because we don't use merge commits, you'll want to avoid it. Rather that using git pull, which by default is a shortcut for git fetch && git merge FETCH_HEAD (docs), you should use git fetch and then git rebase.

First, fetch changes from Zulip's upstream repository you configured in the step above:

$ git fetch upstream

Next, checkout your master branch and rebase it on top of upstream/master:

$ git checkout master
Switched to branch 'master'

$ git rebase upstream/master

This will rollback any changes you've made to master, update it from upstream/master, and then re-apply your changes. Rebasing keeps the commit history clean and readable.

When you're ready, push your changes to your remote fork. Make sure you're in branch master and the run git push:

$ git checkout master
$ git push origin master

You can keep any branch up to date using this method. If you're working on a feature branch (see next section), which we recommend, you would change the command slightly, using the name of your feature-branch rather than master:

$ git checkout feature-branch
Switched to branch 'feature-branch'

$ git rebase upstream/master

$ git push origin feature-branch

Work on a feature branch

One way to keep your work organized is to create a branch for each issue or feature. Recall from how Git is different that Git is designed for lightweight branching and merging. You can and should create as many branches as you'd like.

First, make sure your master branch is up-to-date with Zulip upstream (see how).

Next, from your master branch, create a new tracking branch, providing a descriptive name for your feature branch:

$ git checkout master
Switched to branch 'master'

$ git checkout -b issue-1755-fail2ban
Switched to a new branch 'issue-1755-fail2ban'

Alternatively, you can create a new branch explicitly based off upstream/master:

$ git checkout -b issue-1755-fail2ban upstream/master
Switched to a new branch 'issue-1755-fail2ban'

Now you're ready to work on the issue or feature.

Run linters and tests locally

In addition to having CircleCI run tests and linters each time you push a new commit, you can also run them locally. See testing for details.

Stage changes

Recall that files tracked with Git have possible three states: committed, modified, and staged.

To prepare a commit, first add the files with changes that you want to include in your commit to your staging area. You add both new files and existing ones. You can also remove files from staging when necessary.

Get status of working directory

To see what files in the working directory have changes that have not been staged, use git status.

If you have no changes in the working directory, you'll see something like this:

$ git status
On branch issue-123
nothing to commit, working directory clean

If you have unstaged changes, you'll see something like this:

On branch issue-123
Untracked files:
  (use "git add <file>..." to include in what will be committed)

        newfile.py

nothing added to commit but untracked files present (use "git add" to track)

Stage additions with git add

To add changes to your staging area, use git add <filename>. Because git add is all about staging the changes you want to commit, you use it to add new files as well as files with changes to your staging area.

Continuing our example from above, after we run git add newfile.py, we'll see the following from git status:

On branch issue-123
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        new file:   newfile.py

You can view the changes in files you have staged with git diff --cached. To view changes to files you haven't yet staged, just use git diff.

If you want to add all changes in the working directory, use git add -A (documentation).

You can also stage changes using your graphical Git client.

If you stage a file, you can undo it with git reset HEAD <filename>. Here's an example where we stage a file test3.txt and then unstage it:

$ git add test3.txt
On branch issue-1234
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        new file:   test3.txt

$ git reset HEAD test3.txt
$ git status
On branch issue-1234
Untracked files:
  (use "git add <file>..." to include in what will be committed)

        test3.txt

nothing added to commit but untracked files present (use "git add" to track)

Stage deletions with git rm

To remove existing files from your repository, use git rm (documentation). This command can either stage the file for removal from your repository AND delete it from your working directory or just stage the file for deletion and leave it in your working directory.

To stage a file for deletion and remove it from your working directory, use git rm <filename>:

$ git rm test.txt
rm 'test.txt'

$ git status
On branch issue-1234
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        deleted:    test.txt

$ ls test.txt
ls: No such file or directory

To stage a file for deletion and keep it in your working directory, use git rm --cached <filename>:

$ git rm --cached test2.txt
rm 'test2.txt'

$ git status
On branch issue-1234
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        deleted:    test2.txt

$ ls test2.txt
test2.txt

If you stage a file for deletion with the --cached option, and haven't yet run git commit, you can undo it with git reset HEAD <filename>:

$ git reset HEAD test2.txt

Unfortunately, you can't restore a file deleted with git rm if you didn't use the --cache option. However, git rm only deletes files it knows about. Files you have never added to git won't be deleted.

Commit changes

When you've staged all your changes, you're ready to commit. You can do this with git commit -m "My commit message." to include a commit message.

Here's an example of committing with the -m for a one-line commit message:

$ git commit -m "Add a test commit for docs."
[issue-123 173e17a] Add a test commit for docs.
 1 file changed, 1 insertion(+)
 create mode 100644 newfile.py

You can also use git commit without the -m option and your editor to open, allowing you to easily draft a multi-line commit message.

How long your commit message should be depends on where you are in your work. Using short, one-line messages for commits related to in-progress work makes sense. For a commit that you intend to be final or that encompasses a significant amount or complex work, you should include a longer message.

Keep in mind that your commit should contain a 'minimal coherent idea' and have a quality commit message. See Zulip docs Commit Discipline and Commit messages for details.

Here's an example of a longer commit message that will be used for a pull request:

Integrate Fail2Ban.

Updates Zulip logging to put an unambiguous entry into the logs such
that fail2ban can be configured to look for these entries.

Tested on my local Ubuntu development server, but would appreciate
someone testing on a production install with more users.

Fixes #1755.

The first line is the summary. It's a complete sentence, ending in a period. It uses a present-tense action verb, "Integrate", rather than "Integrates" or "Integrating".

The following paragraphs are full prose and explain why and how the change was made. It explains what testing was done and asks specifically for further testing in a more production-like environment.

The final paragraph indicates that this commit addresses and fixes issue #1755. When you submit your pull request, GitHub will detect and link this reference to the appropriate issue. Once your commit is merged into zulip/master, GitHub will automatically close the referenced issue. See Closing issues via commit messages for details.

Make as many commits as you need to to address the issue or implement your feature.

Push your commits to GitHub

As you're working, it's a good idea to frequently push your changes to GitHub. This ensures your work is backed up should something happen to your local machine and allows others to follow your progress. It also allows you to [work from multiple computers][self-multiple-computers] without losing work.

Pushing to a feature branch is just like pushing to master:

$ git push origin <branch-name>
Counting objects: 6, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (6/6), 658 bytes | 0 bytes/s, done.
Total 6 (delta 3), reused 0 (delta 0)
remote: Resolving deltas: 100% (3/3), completed with 1 local objects.
To git@github.com:christi3k/zulip.git
 * [new branch]      issue-demo -> issue-demo

If you want to see what git will do without actually performing the push, add the -n (dry-run) option: git push -n origin <branch-name>. If everything looks good, re-run the push command without -n.

If the feature branch does not already exist on GitHub, it will be created when you push and you'll see * [new branch] in the command output.

Examine and tidy your commit history

Examining your commit history prior to submitting your pull request is a good idea. Is it tidy such that each commit represents a minimally coherent idea (see commit discipline)? Do your commit messages follow Zulip's style? Will the person reviewing your commit history be able to clearly understand your progression of work?

On the command line, you can use the git log command to display an easy to read list of your commits:

$ git log --all --graph --oneline --decorate

* 4f8d75d (HEAD -> 1754-docs-add-git-workflow) docs: Add details about configuring Travis CI.
* bfb2433 (origin/1754-docs-add-git-workflow) docs: Add section for keeping fork up-to-date to Git Guide.
* 4fe10f8 docs: Add sections for creating and configuring fork to Git Guide.
* 985116b docs: Add graphic client recs to Git Guide.
* 3c40103 docs: Add stubs for remaining Git Guide sections.
* fc2c01e docs: Add git guide quickstart.
| * f0eaee6 (upstream/master) bug: Fix traceback in get_missed_message_token_from_address().

Alternatively, use your graphical client to view the history for your feature branch.

If you need to update any of your commits, you can do so with an interactive rebase. Common reasons to use an interactive rebase include:

squashing several commits into fewer commits
splitting a single commit into two or more
rewriting one or more commit messages

There is ample documentation on how to rebase, so we won't go into details here. We recommend starting with GitHub's help article on rebasing and then consulting Git's documentation for git-rebase if you need more details.

If all you need to do is edit the commit message for your last commit, you can do that with git commit --amend. See Git Basics - Undoing Things for details on this and other useful commands.

Force-push changes to GitHub after you've altered your history

Any time you alter history for commits you have already pushed to GitHub, you'll need to prefix the name of your branch with a +. Without this, your updates will be rejected with a message such as:

$ git push origin 1754-docs-add-git-workflow
To git@github.com:christi3k/zulip.git
 ! [rejected] 1754-docs-add-git-workflow -> 1754-docs-add-git-workflow (non-fast-forward)
error: failed to push some refs to 'git@github.com:christi3k/zulip.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

Re-running the command with +<branch> allows the push to continue by re-writing the history for the remote repository:

$ git push origin +1754-docs-add-git-workflow
Counting objects: 12, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (12/12), done.
Writing objects: 100% (12/12), 3.71 KiB | 0 bytes/s, done.
Total 12 (delta 8), reused 0 (delta 0)
remote: Resolving deltas: 100% (8/8), completed with 2 local objects.
To git@github.com:christi3k/zulip.git
 + 2d49e2d...bfb2433 1754-docs-add-git-workflow -> 1754-docs-add-git-workflow (forced update)

This is perfectly okay to do on your own feature branches, especially if you're the only one making changes to the branch. If others are working along with you, they might run into complications when they retrieve your changes because anyone who has based their changes off a branch you rebase will have to do a complicated rebase.

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