doc: add new git tutorial

So far we've gotten 112 comments from 30ish beta testers who have tried to learn Git for the first using this tutorial. Most of them were able to finish it successfully. By far the most common piece of feedback was that people want to learn more about collaboration and branching. I've written a draft of a tutorial on branching, but this is already quite a lot of words so definitely we can't cover it in this series.

I don't know if it's possible to get this merged quickly, but if it were I think it would be amazing since people are so eager for a tutorial on branching. If we spend a huge amount of time revising this I think there's a real risk I'll run out of funding before we have time to write about branching. Ideally I think it would be great if we could merge a "good enough" version and then have a way on the website for users to give feedback on it, so that we can later incorporate that feedback and iteratively make it better over time.

Thanks to Paula, Agavi, Ken Wells, Michael / Chgowiz, Ishmaeel, and all 20 or so other test readers.

changes in v3: (v2 was the "first" real version since v1 was a WIP)

* Say that the tutorial supports any version above 2.23.0, when git switch was introduced, since the next part of the tutorial on branches will use git switch
* Mention that on Windows the tutorial will work best in Git Bash for and it might need adapting for PowerShell. (thanks to Ben)
* Add a warning about how Git can dump you into vi, how to handle that situation, and how to write a longer commit message. I tried to strike a balance between lightly suggesting that it might be good to write longer commit messages, while making it clear that you can just use -m"" if you're not ready to navigate the world of editor configuration. I don't think we can use Pro Git here though since it's a bit outdated. (thanks to Ben)
* Add Helped-by: Ben ...
* Add output of "ls ~/.ssh/*.pub" (thanks to a test reader)
* Suggest cat ~/.ssh/whatever.pub to make it clearer how to copy the contents of the file. One of the test readers said this was unclear as well. (thanks to Junio)
* Mention that the public key might not be called ed25519.pub (thanks to Junio)
* Add a short section on the importance of git status
* Fixed the formatting around the headings. Kept it in the same style because I had issues with the docs linter when using == DESCRIPTION (thanks to Junio)
* explain what --set-upstream does (thanks to Ben)
* A few other small phrasing fixes from test readers

non-changes in v3:

* didn't use git config set since the tutorial claims to be compatible with Git 2.23.0
* kept using the term "folders" since my impression is that Mac OS and Windows use the term "folder" and those operating systems are more popular than Linux. I don't think any test readers were confused by this term, though "directories" might be fine too.
* leave git init instead of git init myproject so that folks can use the same process when setting up Git in an existing project

changes in v4:

Make the instructions more Windows-friendly (thanks to Richard Kerry), by:

* mentioning that Git for Windows will ask you to configure a text editor when you install it
* saying that the SSH instructions are Mac/Linux only and suggesting using Git Credential Manager on Windows, and update the instructions for whether to use an HTTPS/SSH URL accordingly
* using "folder" instead of "directory" in a few more places Also:
* Say "bottom left" (thanks to Ben)
* Add a link to how to configure various text editors
https://git-scm.com/book/en/v2/Appendix-C:-Git-Commands-Setup-and-Config#ch_core_editor
(thanks to Ben)

non-changes in v4:

* leave the comment about how vim is "extremely difficult if you're not used to it" alone, I couldn't come up with a better way to communicate it and I really don't want anyone to think that being able to use vim is expected.

changes in v5:

* replace "it" with "GCM" in the commit message
* remove some trailing whitespace the CI on GitHub told me about (make check-docs doesn't seem to check for this)

Julia Evans (2):
doc: remove gittutorial
doc: add new Git tutorial for beginners

 Documentation/gittutorial.adoc | 1051 ++++++++++++++++++--------------
 1 file changed, 589 insertions(+), 462 deletions(-)

base-commit: 47fdf2208c5b94c8cc01c106b8f7c85efb91c926
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2248%2Fjvns%2Fgit-tutorial-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2248/jvns/git-tutorial-v5
Pull-Request: https://github.com/gitgitgadget/git/pull/2248

Range-diff vs v4:

 1:  64d9811539 = 1:  64d9811539 doc: remove gittutorial
 2:  4b40588c90 ! 2:  051b2c4551 doc: add new Git tutorial for beginners

@@ Commit message
giving some instructions for how to translate an HTTPS URL to an SSH URL.
- Use Git Credential Manager for authentication on Windows, since it's
- simpler, SSH auth is a very "unixy" thing to do, and it comes with
+ simpler, SSH auth is a very "unixy" thing to do, and GCM comes with
Git for Windows
- Warn people about how vi is the default text editor and give some instructions for how to escape
@@ -1,2 +1,2 @@
+On Windows, you can skip this step and the next one because Git for +Windows comes with +https://github.com/git-ecosystem/git-credential-manager[Git Credential Manager]
-+to handle logging in.
++to handle logging in.
+
+If you don't already have an SSH key, you'll need to create one. +You can check if you already have an SSH key by running:

gitgitgadget