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Git mini-tutorial

Before starting the tutorial, it is important to clarify definitions of the following for beginners:

  • git commandline tool
    • for running "git commands"
  • Git SCM (source code management) format
    • git repositories are directories of this format
  • Github
    • projects are hosted at this publicly accessible collaboration platform which is built around Git repositories

This is a "just the steps" mini-tutorial. It is aimed at first-time users of Git, or relatively new users wanting to know the steps this project uses in the context of Github. If any step is confusing it should be easy to find details & explanations by searching Github documentation, or googling the command and especially looking at stackoverflow answers that come up for it. The instructions below are for the example-case of a first-time contributor adding a language to the translation-table.

Text with preceding ## is either for you to replace, for example:

a_variable=## Replace this with your favourite food

becomes:

a_variable=banana

or instructions to follow, for example:

echo "silly command"
## Repeat the above 3 times

becomes:

echo "silly command"
echo "silly command"
echo "silly command"
  1. Ensure you have the git commandline tool installed and usable in a shell. If on Windows and you haven't already installed a "POSIX compatible" shell ("command line"), the simplest thing is to install the bundled git package which includes its own shell.
  2. In your browser, logged into Github, in the top-right corner of this repo, click the Fork icon which will create your own fork.
  3. In the shell do the following. Setting the variables at the beginning is just to make this tutorial more readable, you can obviously enter the text directly each time instead of using variables if you prefer: 
    common_dir=## Replace this with a common directory to hold your repositories
user=## Replace this with your github username
lang=## Replace this with your translation language

mkdir -p "${common_dir}"
cd "${common_dir}"
  4. In the shell clone your fork to a local directory. For the simpler https method (but which requires you to enter your password whenever you do remote actions), do: 
    git clone https://github.com/${user}/GoogleContactsEventsNotifier.git
    If you optionally want to be more advanced and use ssh instead of https then do the documented steps for adding your ssh public-key to your github account if you haven't already, and then do: 
    git clone [email protected]:${user}/GoogleContactsEventsNotifier.git
  5. In the shell do the following to create the new branch with your changes. You will need to know which existing upstream branch it should be based on. Although basing it on the upstream master branch is usually what you want, sometimes you may need to base it on an "upstream feature/fix branch" which the maintainers will later merge to their master branch (if in doubt ask the maintainers): 
    upstream_branch=## Replace this with the upstream branch

cd GoogleContactsEventsNotifier
git checkout -b ${lang}-translations ${upstream_branch}
## Edit code.gs in text editor, find the commented text at the bottom of the
## translation-table, create the translations as per the instructions there,
## then save & exit.
git add code.gs
git commit -m "${lang} translations"
git push origin ${lang}-translations
  6. In your browser, logged into Github, visit your forked repo at https://github.com/${user}/GoogleContactsEventsNotifier, and there will be a notification about a recently added branch, asking if you wish to open it as a Pull Request. Do that, remembering that if the Pull Request is based on an upstream branch other than the default master, then you should select that while opening it.

Below are other steps you might need to take sometimes. Don't worry though, if any of them are too intimidating the upstream maintainers can usually make the changes to your branch for you on request - when they have time! - and you will still retain "authorship" of your commits:

  • If upstream's copy of ${upstream_branch} has been modified or had new commits added since you created your commits the maintainers may ask you to rebase your branch on it to update your PR (so they can merge it cleanly). This means if you haven't already added the upstream repo as a "remote" you'd first need to do: 
    git remote add upstream https://github.com/GioBonvi/GoogleContactsEventsNotifier.git
    then either way you'd need to do: 
    git checkout ${upstream_branch}
git pull upstream ${upstream_branch}
git checkout ${lang}-translations
git rebase ${upstream_branch}
git push --force origin ${lang}-translations
  • If the upstream maintainers ask you to fix a commit (e.g. for a typo), if your PR has only one commit you can do the following: 
    git checkout ${lang}-translations
## Edit code.gs in text editor, save & exit.
git add code.gs
git commit --amend
git push --force origin ${lang}-translations
    If your PR includes more than one commit (usually never, if just translations for a basic lookup table) then instead of the above you need to do: 
    git checkout ${lang}-translations
git fetch upstream ${upstream_branch}
git rebase -i ${upstream_branch}
## For any commit that needs editing change the beginning of the line from
## "pick" to "edit", then save & exit.
## -- loop starts here --
## Edit code.gs in text editor, save & exit
git add code.gs
git commit --amend
git rebase --continue
## -- loop ends here --
## Do the above loop until the rebase finishes.
git push --force origin ${lang}-translations
  • If the upstream maintainers ask you to squash several commits into one, then do: 
    git checkout ${lang}-translations
git fetch upstream ${upstream_branch}
git rebase -i ${upstream_branch}
## For any commit which should be included into its previous commit, change
## the beginning of the line from "pick" to "squash" - or to "fixup" if you
## just want to use the first commit-message in the log - then save & exit.
## If you used "squash" you'll be asked to edit the combined commit-message.
git push --force origin ${lang}-translations

In the above steps:

  • The git push --force is because you are rewriting history which is usually a big no-no for a "real public-facing branch", but this is just a temporary PR-branch, so no-one should be relying on its history anyway.
  • In the unlikely event that you ever have a "merge conflict" during git rebase (either because you've made conflicting changes to your own earlier commits during git rebase -i or if you encounter conflicting changes during git rebase against an upstream branch), then you need to edit code.gs again to cleanup wherever there are lines that look like: 
    <<<<<<< XXXXX:branch-name
# First conflicting updated line(s)...
=======
# Second conflicting updated line(s)...
>>>>>>> YYYYY:branch-name
    to replace them with a single correct version (whether replacing with one of them or a manually edited combination of both) removing the <<<<<<<, >>>>>>>, and ======= lines too, and then do: 
    git add code.gs
git rebase --continue
    This is quite complicated though, so if you ever need to do it you can ask for help or google for instructions first.

There are many more aspects to git for the adventurous, but they are out of scope for this intro.