Exercise: Managing a project with Git

Managing a project with Git

• Clone a project and read its history.
• Review, commit and push a tested change.
• Keep a password file and tool output out of the repository.
• Combine a teammate's commit with yours after a rejected push.

Prerequisites: Complete control-node setup and the Git lesson. Run commands as student on workstation.

From ~/workflow-git, run:

lab grade workflow-git

The grader checks the clone, the history, that everything is committed and pushed, the ignore rule, and /etc/motd on both web servers. It never changes your project or the hosts.

Change the contact address in a new commit, push it, then use git log -p -1 to show exactly what your last commit changed. Use git show HEAD~1:templates/motd.j2 to print the previous version of the template without changing your files.

The grader checks the original contact line, so a changed address intentionally fails that check.

Work in a clone of the shared web-motd project, in ~/workflow-git.

• Add the line Contact: ops@lab.example.com to the MOTD template, apply it to both web servers, and commit and push the change.
• Create a vault password file named vault-pass (mode 0600) in the project. Make sure Git never offers to commit it, nor the ansible-navigator.log file that navigator writes on every run.
• A teammate adds the line Check: run the playbook twice; the second run reports changed=0. to README.md and pushes it while you are working. Combine their commit with yours and push the result.
• Finish with a clean working tree that matches the remote.

Tell Git who you are

Set your identity and how git pull combines histories. These settings are stored in ~/.gitconfig and apply to every repository you use as student:

[student@workstation ~]$ git config --global user.name 'Student'
[student@workstation ~]$ git config --global user.email 'student@workstation.lab.example.com'
[student@workstation ~]$ git config --global pull.rebase false
[student@workstation ~]$ git config --global --list
user.name=Student
user.email=student@workstation.lab.example.com
pull.rebase=false

Clone the project

Start the exercise, then clone the remote into the empty project directory. The . at the end means "clone into the current directory":

[student@workstation ~]$ lab start workflow-git
[student@workstation ~]$ cd ~/workflow-git
[student@workstation workflow-git]$ git clone ~/git-repos/ops/web-motd.git .
Cloning into '.'...
done.
[student@workstation workflow-git]$ ls
ansible.cfg  inventory  motd.yml  README.md  templates
[student@workstation workflow-git]$ git log --oneline
de3139f Warn that the MOTD is managed
71096de Add the MOTD project
[student@workstation workflow-git]$ git status
On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

Your commit IDs differ: they include the time each commit was made. Read motd.yml and templates/motd.j2. The play deploys the template to /etc/motd on servera and serverb.

Run the project as it is

Before you change anything, check that the project works:

[student@workstation workflow-git]$ ansible-navigator run motd.yml -m stdout
...output omitted...
servera.lab.example.com    : ok=2    changed=1    unreachable=0    failed=0  ...
serverb.lab.example.com    : ok=2    changed=1    unreachable=0    failed=0  ...
[student@workstation workflow-git]$ git status --short
?? ansible-navigator.log

Navigator wrote a log file into the project. Git lists it with ??: a file it does not track. You will deal with it in a later step; do not commit it.

Make, test and commit a change

Add the contact line to the template, review the change, apply it, and check one host:

[student@workstation workflow-git]$ echo 'Contact: ops@lab.example.com' >> templates/motd.j2
[student@workstation workflow-git]$ git diff
diff --git a/templates/motd.j2 b/templates/motd.j2
index dd8ce2e..d3a141a 100644
--- a/templates/motd.j2
+++ b/templates/motd.j2
@@ -1,2 +1,3 @@
 Welcome to {{ inventory_hostname }}.
 This host is managed by Ansible: local changes to this file are overwritten.
+Contact: ops@lab.example.com
[student@workstation workflow-git]$ ansible-navigator run motd.yml -m stdout
...output omitted...
[student@workstation workflow-git]$ ssh devops@servera.lab.example.com cat /etc/motd
Welcome to servera.lab.example.com.
This host is managed by Ansible: local changes to this file are overwritten.
Contact: ops@lab.example.com

It works, so commit it. Stage only the template, check what you staged, then commit and push:

[student@workstation workflow-git]$ git add templates/motd.j2
[student@workstation workflow-git]$ git diff --cached --stat
 templates/motd.j2 | 1 +
 1 file changed, 1 insertion(+)
[student@workstation workflow-git]$ git commit -m 'Add a contact line to the MOTD'
[main 48b3081] Add a contact line to the MOTD
 1 file changed, 1 insertion(+)
[student@workstation workflow-git]$ git push
To /home/student/git-repos/ops/web-motd.git
   de3139f..48b3081  main -> main

A teammate pushes a change

Play the teammate yourself, in a second clone of the same remote. They document the repeat-run check in the README and push it:

[student@workstation workflow-git]$ git clone ~/git-repos/ops/web-motd.git ~/web-motd-teammate
[student@workstation workflow-git]$ cd ~/web-motd-teammate
[student@workstation web-motd-teammate]$ echo 'Check: run the playbook twice; the second run reports changed=0.' >> README.md
[student@workstation web-motd-teammate]$ git commit -am 'Document the repeat-run check'
[student@workstation web-motd-teammate]$ git push
[student@workstation web-motd-teammate]$ cd ~/workflow-git

git commit -a stages every modified tracked file before committing. It never adds untracked files.

Keep the password file and the log out of Git

Your project will use Ansible Vault later, so create its password file now. Git offers it for committing straight away, together with navigator's log:

[student@workstation workflow-git]$ echo 'redhat' > vault-pass
[student@workstation workflow-git]$ chmod 600 vault-pass
[student@workstation workflow-git]$ git status --short
?? ansible-navigator.log
?? vault-pass

Create .gitignore with both names, one per line:

vault-pass
ansible-navigator.log

Now Git only offers the .gitignore file itself. Commit it:

[student@workstation workflow-git]$ git status --short
?? .gitignore
[student@workstation workflow-git]$ git check-ignore -v vault-pass
.gitignore:1:vault-pass	vault-pass
[student@workstation workflow-git]$ git add .gitignore
[student@workstation workflow-git]$ git commit -m 'Keep the vault password and navigator log out of Git'

Combine your work with your teammate's

Push your new commit. The remote has your teammate's commit, which you do not have, so Git refuses:

[student@workstation workflow-git]$ git push
To /home/student/git-repos/ops/web-motd.git
 ! [rejected]        main -> main (fetch first)
error: failed to push some refs to '/home/student/git-repos/ops/web-motd.git'
...output omitted...

Pull their commit. Git merges it with yours in a new merge commit; --no-edit accepts the default message instead of opening an editor. Then push again:

[student@workstation workflow-git]$ git pull --no-edit
From /home/student/git-repos/ops/web-motd
   48b3081..43eabe1  main       -> origin/main
Merge made by the 'ort' strategy.
 README.md | 1 +
 1 file changed, 1 insertion(+)
[student@workstation workflow-git]$ git push
[student@workstation workflow-git]$ git log --oneline --graph
*   eb79d6a Merge branch 'main' of /home/student/git-repos/ops/web-motd
|\
| * 43eabe1 Document the repeat-run check
* | 7590b93 Keep the vault password and navigator log out of Git
|/
* 48b3081 Add a contact line to the MOTD
* de3139f Warn that the MOTD is managed
* 71096de Add the MOTD project

The graph shows the two lines of work, yours and your teammate's, joining in the merge commit. Remove the teammate's clone; its work is safe on the remote:

[student@workstation workflow-git]$ rm -rf ~/web-motd-teammate

Check and grade

Your working tree should be clean and match the remote, with vault-pass and the log still on disk but ignored:

[student@workstation workflow-git]$ git status
On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean
[student@workstation workflow-git]$ ls
ansible.cfg  ansible-navigator.log  inventory  motd.yml  README.md  templates  vault-pass
[student@workstation workflow-git]$ lab grade workflow-git

Every check should pass. When you are done, run lab finish workflow-git.