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3.2 Git cheat sheet
The intent of this section is to get you working on LilyPond quickly. If you want to learn about Git, go read Further Git documentation resources.
Also, these instructions are designed to eliminate the most common problems we have found in using Git. If you already know Git and have a different way of working, great! Feel free to ignore these advice.
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Pulling recent changes
As LilyPond’s source code is continously improved, it is wise to
integrate recent changes into your local copy whenever you start a
working session. On the master
branch (this term is explained
below), run:
git pull
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Viewing the history
Each change is contained in a commit with an explanatory message. To list commits starting from the latest:
git log
Press <Enter> to see more or <Q> to exit.
Start work: make a new branch
The Git workflow is based on branches, which can be viewed as different copies of the source code with concurrent changes that are eventually merged. You start a contribution by creating a branch, freezing the initial state of the source code you will base your work onto. Ultimately, your branch will be merged in master. This latter special branch centralizes all features developed simultaneously and is the source for unstable releases.
Note: Remember, never directly commit to master
.
Let’s pretend you want to add a section to the Contributor’s Guide about using branches. To create a new branch for this:
git branch cg-add-branches
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Switching branches
Switching branches is somehow like “loading a file”, although in
this case it is really “loading a directory and subdirectories
full of files”. The command to use is git checkout
.
git checkout master git checkout cg-add-branches git checkout origin/release/unstable
Branches that begin with origin/
are part of the remote
repository, rather than your local repository, so when you check them
out you get a temporary local branch. Therefore, do not commit to
these either. Always work in a local branch.
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Listing branches
To list local branches:
git branch
If you want remote branches too:
git branch -a
In the output, the current branch is prefixed with a star.
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Staging and committing files
Now edit files. To show a summary of your edits:
git status
For every file that you modified or added, first preview your changes:
git diff file
If everything looks right:
git add file
Then commit your changes:
git commit
A text editor window appears for you to write a commit message. See Writing good commit messages.
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Amending and reverting changes
To add some more changes to the latest commit, stage them using
git add
, then run:
git commit --amend
This also works for rephrasing the commit message.
To revert changes to a file that has not been committed yet:
git checkout filename
To get back to the last commit, discarding all changes:
git reset --hard HEAD
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Uploading your branch for review
To upload the current branch on the remote repository:
git push -u fork cg-add-branches
This sets the remote branch so subsequent pushes are simpler:
git push
The next section covers how to create a merge request from your branch.
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Deleting branches
After the merge request has passed testing and was merged to
master
, or after a failed experiment, you can delete your
local branch.
git checkout master git branch -d cg-add-branches
As a safety measure, this will fail if the commits of
cg-add-branches
are not present in master
. This can be
because you used GitLab to rebase your branch, which modifies the commit
data and changes the hash. If you are sure that the branch is not needed
anymore, replace the -d
on the final line with a -D
instead.
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