en:git [Computergestützte Musikanalyse]

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====== Introduction to Git and GitHub for Musicology Editorial Work ======

===== Why this matters =====

In digital musicology, we often work with files that change over time:
  * digital encoded files (MEI, MusicXML, MIDI, etc.)
  * metadata tables
  * documentation
  * editorial notes
  * scripts for processing musical sources

A common problem is that files get copied, renamed, emailed around, or stored as:
  * ''final.xml''
  * ''final_revised.xml''
  * ''final_revised2.xml''
  * ''final_REAL_final.xml''

This quickly becomes confusing.

**Git** helps us keep a structured history of changes.  
**GitHub** makes it easier to synchronize work between computers and collaborate with others.

For musicological editorial work, this is especially useful because:
  * we need to track who changed what
  * we need to document editorial decisions
  * we often work on the same corpus over long periods
  * we need a safe way to synchronize data across machines
  * we may want to collaborate on corrections

===== Learning goals =====

After this introduction, students should be able to:
  * explain what Git is
  * understand the difference between Git and GitHub
  * create a local Git repository
  * save changes with meaningful commit messages
  * connect a local repository to GitHub
  * synchronize editorial work between computers
  * understand a basic collaboration workflow for MEI and OMR data
  * avoid common mistakes when working with Git

===== What is Git? =====

Git is a **version control system**.

This means it records the history of a folder and its files over time.

With Git, you can:
  * save snapshots of your work
  * see what changed between two versions
  * return to an earlier state
  * work on new ideas without breaking the main version
  * merge work from different collaborators

Git is **not** only for programmers.  
It is useful for any research project where files evolve over time.

===== What is GitHub? =====

GitHub is a web platform built around Git.

Git itself works on your computer.  
GitHub adds:
  * online hosting of repositories
  * synchronization between computers
  * collaboration tools
  * issue tracking
  * pull requests for reviewing changes
  * backup in the cloud

A useful short formula is:

  * **Git = version control**
  * **GitHub = online hosting and collaboration for Git repositories**

===== Core concepts =====

==== Repository ====

A **repository** (or "repo") is a project folder managed by Git.

It contains:
  * your files
  * a hidden Git history
  * information about changes over time

==== Commit ====

A **commit** is a saved snapshot of your work.

A commit should record a meaningful step, for example:
  * corrected clef encoding in measure 1
  * normalized staff labels in manuscript A
  * added measure numbers to MEI files
  * fixed pitch errors in soprano part

==== GitHub remote ====

A **remote** is an online copy of your repository, for example on GitHub.

This lets you:
  * upload your local work
  * download changes made elsewhere
  * keep multiple computers synchronized

==== Push and pull ====

  * **push** = send your local commits to GitHub
  * **pull** = download changes from GitHub to your local machine

==== Branch ====

A **branch** is a parallel line of work.

Branches are useful when:
  * testing a new editorial strategy
  * correcting one source separately
  * working on a feature without changing the stable main version

===== Why Git is useful for OMR and MEI editorial work =====

Git works especially well when files are text-based.

MEI files are XML, so Git can track line-by-line changes very well.

This means Git can help you see:
  * where measures were changed
  * where attributes were added or removed
  * where note encodings were corrected
  * which editor made which change

===== Important limitation: binary files =====

Git works best with **plain text files**:
  * ''.mei''
  * ''.xml''
  * ''.csv''
  * ''.txt''
  * ''.md''
  * code files such as ''.py''

Git works less well with large binary files such as:
  * ''.pdf''
  * ''.docx''
  * ''.png''
  * ''.jpg''
  * ''.tif''

This does not mean you cannot store such files in a repository, but:
  * changes are harder to compare
  * repositories become larger
  * collaboration becomes less efficient

===== Installing Git =====

What is needed:
  * Git installed on computer
  * a GitHub account
  * optionally GitHub Desktop, if you prefer a graphical interface

For long-term understanding, command line Git is better.
For quick adoption, GitHub Desktop may be easier.

Mei-friend has a sophisticated GitHub integration which we'll probably use most of the time, but git syntax is universally usable in all tools/environments.

===== First-time Git setup =====

After installing Git, set your name and email in the terminal:

<code bash>
git config --global user.name "Your Name"
git config --global user.email "your.email@example.org"
</code>

This identifies your commits.

Check the configuration:

<code bash>
git config --global --list
</code>

===== Starting a repository =====

Move into your project folder:

<code bash>
cd path/to/music-edition-project
</code>

Initialize Git:

<code bash>
git init
</code>

Now Git is tracking this folder as a repository.

===== Checking repository status =====

The most important command for beginners is:

<code bash>
git status
</code>

This shows:
  * which files are new
  * which files were changed
  * which files are ready to be committed

Students should get used to running ''git status'' very often.

===== Adding files =====

To prepare all current changes for a commit:

<code bash>
git add .
</code>

To add one specific file:

<code bash>
git add data/mei/motet_01.mei
</code>

===== Making a commit =====

After adding files, save a snapshot:

<code bash>
git commit -m "Corrected note durations in motet_01"
</code>

A good commit message is:
  * short
  * specific
  * meaningful

Good examples:
  * ''Corrected mensuration encoding in Kyrie''
  * ''Normalized staff labels in source B''
  * ''Fixed barline errors in movement 3''
  * ''Added editorial note on unclear accidentals''

Bad examples:
  * ''changes''
  * ''update''
  * ''stuff''
  * ''final''

===== Connecting to GitHub =====

Create an empty repository on GitHub.

Then connect your local repository to it:

<code bash>
git remote add origin https://github.com/USERNAME/REPOSITORY.git
</code>

Check that the remote was added:

<code bash>
git remote -v
</code>

===== Uploading your work to GitHub =====

If your main branch is called ''main'':

<code bash>
git branch -M main
git push -u origin main
</code>

After that, future uploads are usually just:

<code bash>
git push
</code>

===== Downloading changes from GitHub =====

Before you start working, download any new changes:

<code bash>
git pull
</code>

This is especially important if:
  * you work on multiple computers
  * a collaborator may have updated the repository
  * you edited files on GitHub directly

===== A minimal daily workflow =====

<code bash>
git pull
git status
git add .
git commit -m "Describe the editorial change"
git push
</code>

This can be explained as:

  * ''pull'' before work
  * edit files
  * ''status'' to inspect changes
  * ''add'' to stage them
  * ''commit'' to record them
  * ''push'' to synchronize them

===== Collaboration basics =====

When multiple people work on one repository, Git can help organize collaboration.

A simple shared workflow:
  * each editor pulls before starting
  * each editor commits small changes regularly
  * each editor writes clear commit messages
  * each editor pushes finished work
  * the team agrees on folder structure and editorial conventions

For slightly more advanced collaboration, use:
  * branches
  * pull requests
  * code review or editorial review on GitHub

===== Branches for safer experimentation =====

Branches are useful when you want to try something without changing the stable version.

Example uses:
  * testing a new encoding strategy
  * revising one source separately
  * trying automated clean-up on MEI files
  * preparing a larger correction batch

Create a new branch:

<code bash>
git checkout -b revise-source-A
</code>

Work and commit as usual.

Later, the branch can be merged into the main branch.

===== Merge conflicts =====

A **merge conflict** happens when Git cannot automatically combine two competing changes.

Example:
  * two people edit the same passage in the same MEI file
  * both commit their changes
  * Git does not know which version should win

This is normal and not a disaster.

The usual solution is:
  - inspect the conflicting file
  - decide which reading to keep
  - edit the file manually
  - save the corrected version
  - commit the resolution

For beginners, the best prevention is:
  * communicate who edits which files
  * make small commits
  * pull frequently
  * avoid long unsynchronized work sessions

===== GitHub features that are useful for editorial projects =====

Useful GitHub features include:

==== Issues ====

Use issues to track:
  * uncertain readings
  * missing metadata
  * files needing review
  * recurring OMR errors
  * editorial questions

==== Pull requests ====

A pull request lets someone propose changes before merging them.

This is useful for:
  * checking corrections before accepting them
  * discussing editorial choices
  * reviewing larger changes

==== History and blame ====

GitHub also allows you to inspect file history and see who last changed a line.

This can be very helpful when asking:
  * when was this corrected?
  * who changed this encoding?
  * why was this element added?

===== Glossary =====

^ Term ^ Meaning ^
| Git | Version control system |
| GitHub | Online platform for hosting Git repositories |
| Repository | A project folder tracked by Git |
| Commit | A saved snapshot of changes |
| Push | Upload local commits to GitHub |
| Pull | Download changes from GitHub |
| Branch | A separate line of development |
| Merge | Combine changes from different branches |
| Conflict | A situation where Git cannot automatically combine changes |