Using Git

Setup

• Set your name with git

git config --global user.name "Ivan Ivanov"
git config --global user.email "[email protected]"

• Go to https://github.com/settings/ssh and add your public SSH key (GitHub Help).

• Clone the repository

git clone [email protected]:MariaDB/server.git
cd server

• Run git branch to check that you're working on MariaDB 10.1:

server $ git branch
* 10.1

• Config repository pull and alias for fast forward:

git config pull.ff only
git config --global alias.ff "merge --ff-only"

Commit comments

In git commit messages are normally formatted as

subject

body
more body
...

That is, the first line is considered a *subject*, much like email subject. Many git commands and pages on github only show the commit subject, not the complete comment. After the subject goes an empty line, then the detailed description of the comment. Please, structure your commit comments this way, don't forget the empty line.

Branches

This is an important concept, and git branches do not have equivalents in bzr.

In Bazaar, we all used to have one shared repository, within which there were many branches. This seems to be impossible with git?

In Git, each repository has only one branch that is currently checked out.

git branch

List existing branches

To see which branches exists locally and remotely:

git branch --all

To move to work on a specific branch

git checkout branch-name

Note that if the output from git branch --all is remotes/origin/XXX you should just use XXX as branch name.

Making a local copy of a branch (like bzr clone)

branch clone old_directory new_directory
cd new_directory
git remote set-url origin [email protected]:MariaDB/server.git
git pull

Remove last commit from a branch

git reset --hard HEAD^ 

Fetch a branch someone has done a rebase on

If you get the following error on pull:

shell>  git pull
X11 forwarding request failed on channel 0
fatal: Not possible to fast-forward, aborting.

Instead of removing your copy and then clone, you can do:

git reset --hard origin/##branch-name##

Other things about branches

• Note: branches whose names start with bb- are automatically put into the buildbot.

Equivalents for some bzr commands

CAVEAT UTILITOR. Check the manual before running!

• bzr status is git status
• bzr diff is git diff
• bzr log is git log
• bzr revert is git reset --hard
• bzr revert filename is git checkout filename
• bzr parent is git remote -v (but there are more detailed commands)
• bzr parent to-default-mariadb-repo git remote set-url origin [email protected]:MariaDB/server.git
• bzr push is git push REMOTENAME BRANCHNAME. REMOTENAME is typically "origin", for example: git push origin HEAD:10.3-new-feature. The HEAD: stands for "from current branch".
• bzr clean-tree --ignored is git clean -Xdf (note the capital X!)
• bzr root is git rev-parse --show-toplevel
• bzr missing --mine-only is git cherry -v origin (kind-of).

GUIs

• bzr gcommit is git citool
• bzr viz is gitk
• bzr gannotate is git gui blame

Commit emails

In the MariaDB project, it is a good idea (and a long tradition since MySQL Ab) to have all your commits sent to a [email protected] mailing list. It allows others to follow the progress, comment, etc.

A script and instructions on how to setup commit triggers in Git are here: http://bazaar.launchpad.net/~maria-captains/mariadb-tools/trunk/files/head:/git_template/ . Jira task for commit trigger was MDEV-6278.

Attributing code to someone else

If you add code on behalf of someone else, please attribute the code to the original author:

• Run git citool and move changed files to staged.
• Don't commit, abort instead
• run git commit --author="Original author name <email_address>"

The above is needed as git citool can't handle the --author option.

Examples

Diff for last commit

git show

Applying new code from main tree to a branch

You are working on a branch (NEW_FEATURE) and would like to have into that branch all changes from the main branch (10.1).

git checkout 10.1
git pull
git checkout NEW_FEATURE
git rebase 10.1

Applying a bugfix in the main branch

You've just fixed and committed a bug in the main 10.1 branch and want to merge it with the latest 10.1. Often a rebase is better in this case. Assuming your current checked out branch is 10.1:

git fetch origin
git rebase origin/10.1

This will work even if you have done multiple commits in your local 10.1 tree.

Dealing with conflicts when one tries to push

What to do when you have fixed a bug in the main tree but notices that someone has changed the tree since you pulled last time. This approach ensures that your patch is done in one block and not spread out over several change sets.

git clone 10.1  
cd 10.1
< fix a bug here>
git citool
git push
# ^ and the above fails, because someone has pushed to 10.1 in between
git branch tmp
# ^ copy our work to branch named 'tmp'
get checkout 10.1
git reset --hard HEAD^ 
# ^ remove our work from '10.1' local branch'
git pull 
# ^ get changes from remote
git checkout tmp
git rebase 10.1
# ^ switch to 'tmp' and try to rebase 'tmp' branch on top of 10.1 branch.
#   here you will be asked to merge if necessary
git checkout 10.1
git pull --ff . tmp
# ^ switch back to the '10.1' branch, and pull from 'tmp' branch. 
git branch -D tmp
#^ this removes the tmp. branch
git push

Finding in which MariaDB version a commit exist

sh> git tag --contain e65f667bb60244610512efd7491fc77eccceb9db
mariadb-10.0.30
mariadb-10.1.22
mariadb-10.1.23
mariadb-10.2.5
mariadb-10.3.0
mariadb-galera-10.0.30

See also

• http://agateau.com/talks/2010/git-for-bzr-users_uds-natty/git-for-bzr-users.pdf
• Sergei's "Using GIT" presentation. Malaga Meeting, January 2015