dev:git [~wiki]

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====== git ======

Git is a code [[vcs|Version Control System]].

Useful resources:
  * [[https://ohshitgit.com/|"Oh shit, git!"]]
  * [[https://github.com/git-tips/tips|Git Tips]] on Github
  * [[tools|Tools for Developers]]
  * [[https://www.reddit.com/r/git/|/r/git]]

===== common tasks =====

^ reset changes of specific file | ''%%git checkout -- filename%%'' |
^ undo all changes since last commit | ''%%git reset --hard%%'' |
^ merge multiple commits\\ ([[http://de.gitready.com/advanced/2009/02/10/squashing-commits-with-rebase.html|tutorial]]) | ''git rebase -i'' |
^ show remote repositories | ''git remote'' |

==== add file after commit ====
Sometimes you remember that you have to add a file to the commit you just made.

If you want to add a file to your commit after you already committed the changes:

<code bash>
git add <files>
git commit --amend
</code>

This lets you edit the commit description after you committed the changes.

If you don't want to change the commit message: ''%%git commit --amend --no-edit%%''

===== Learn Git =====
  * [[https://learngitbranching.js.org|Learn Git Branching]] – interactive visual Git tutorial.
  * [[https://git-scm.com/book/en/v2|Pro Git book]] (S. Chacon, B. Straub 2014. Apress)

===== set author =====
<code bash>
git config user.name "John Doe"
git config user.email "john@doe.org"
</code>

===== foreign repositories =====

==== just merge ====

<code bash># I want to make sure my master is in sync with the upstream master
git checkout -b merge-patches master
# first pull request
git pull --no-ff https://github.com/user1/repo.git master
# second pull request
git pull --no-ff https://github.com/user2/repo.git branch1</code>

==== add as remote ====

<code bash>
git remote add upstream path/to/repository.git
# get all refs and objects so your git knows what it can do
git fetch --all
</code>

You can merge foreign branches:

<code bash>
git merge upstream/master
</code>

==== foreign Pull Requests from Github as refs ====

<file - .git/config>
[remote "origin"]
    # add this line
    fetch = +refs/pull/*/head:refs/remotes/origin/pr/*
</file>

then execute:

<code bash>
# get refs
git fetch --all

# merge pull request with ID 999
git checkout pr/999
</code>

([[https://gist.github.com/piscisaureus/3342247|Source]])

===== push new branch =====

<code bash># change to branch to be added
git checkout master
# push it to the repo
git push -u origin master</code>

===== push into non-empty origin/master =====

//Error: [remote rejected] master -> master (branch is currently checked out)//

<code bash>
# push to new branch on remote
git push origin master:refs/heads/upload
# on remote machine
git merge upload
git branch -d upload
</code>

=== Alternative: allow update of local branch ===

  git config --local receive.denyCurrentBranch updateInstead

([[http://stackoverflow.com/questions/2816369/git-push-error-remote-rejected-master-master-branch-is-currently-checked|source]])

==== merge two unrelated repositories ====
If you have two repositories which don't have a common origin, you can still merge them. If you try to do so via simple ''git pull'', you may get the error ''fatal: refusing to merge unrelated histories''. This is because git can't find a commit to base its merge on.

<code bash>
git remote add some-old-repo https://github.com/user/some-old-repo.git
git pull --allow-unrelated-histories some-old-repo master
git status -s
</code>

([[https://www.alexkras.com/git-merg-two-or-more-repositories-and-keeping-history/|source]])

===== manage dotfiles with git =====

<code>
echo "*" >> ~/.gitignore
git add -f .gitignore
</code>

^ dotfile hinzufügen | ''git add -f .dotfile'' |

=== on the target peer ===
<code>
echo "*" >> ~/.gitignore
</code>

^ initialise | git init |
^ add remote | git remote add hostname:~ |
^ fetch files | git fetch --all |
^ replace existing | git reset --hard origin/master |

([[https://lrvick.net/blog/syncing_dotfiles_with_git/|Source]])

===== Submodules =====
^ get submodules when switched to branch with submodules | ''git submodule update'' |

===== Troubleshooting =====

==== I copied a git repository from Linux/macOS to Windows and now it shows all files as changed! ====
Do a "git diff" on any file. What do you see?

=== The permissions have all changed! ===
<code bash>git config core.filemode false</code>

=== The whole file changed with weird ^ characters! ===
These are the line endings. Automatically adjust it to CRLF line endings with:
<code bash>git config --global core.autocrlf true</code>

==== unable to migrate objects to permanent storage ====
Your permissions may be wrong. Check if any of the remote files in `.git` are not owned by the user you're connecting with. ([[https://stackoverflow.com/questions/65033831/unable-to-migrate-objects-to-permanent-storage|source]])

==== git@github.com: Permission denied (publickey) ====
If you just want to clone a public repo with history from GitHub, don't use the ''git'' username like with ''%%git clone git@github.com:radicle-dev/radicle-upstream.git%%'', but rather the ''%%git://%%'' __protocol__:

<code bash>
git clone git://github.com/radicle-dev/radicle-upstream.git
</code>

===== Secrets =====
Store passwords or other information you don't want to accidentally leak somewhere else than in your git repository.

Use a secrets storage for this. You can use [[https://git-secret.io/|git-secret]], [[https://github.com/StackExchange/blackbox|blackbox]] or [[https://www.vaultproject.io/|Hashicorp Vault]] for this.

===== Articles =====
Some random articles about how to use Git in a regular or innovative way.

  * [[https://thenewstack.io/beyond-code-control-git-for-everything/|Beyond Code Control: Git for Everything]] (A. Schmunk, 2019)
  * [[https://medium.com/@dis_is_patrick/git-for-non-programmers-49c85d3f647d|Git for non-programmers]] (2014)
  * [[https://opensource.com/article/19/4/write-git|How writers can get work done better with Git]] (S. Kenlon. Opensource.com, 2019)

===== Videos =====
  * [[https://www.youtube.com/watch?v=wpISo9TNjfU|Git vs. GitHub: What's the difference?]] (2020, Nathan Hekman, IBM Technology)

===== Tools =====
Useful programs to make life with Git easier or adding functionality to Git.

  * [[https://github.com/costerwi/rezip|ReZip]] – commit ZIP files to Git.
  *