Merge pull request #62055 from apple/maxd/git-started

HowToGuides/GettingStarted: require Git 2.x

Trying to run update-checkout with Git 1.8.3.1 fails during rebasing. Git 2.38 works fine. Additionally, looks like Git 1.x requires committer name and email to be set during rebasing, which also causes errors. We should recommend Git 2.x explicitly to make sure new contributors don't get confused by this.

Author: MaxDesiatov

docs/HowToGuides/GettingStarted.md

@@ -45,12 +45,15 @@ toolchain as a one-off, there are a couple of differences:
    system. Experimental instructions for Windows are available under
    [Windows.md](/docs/Windows.md).
 2. Python 3: Several utility scripts are written in Python.
-3. Disk space:
+3. Git 2.x to check out the sources. We find that older versions of Git
+   can't successfully check out all of the required repositories or
+   fail during a rebase when switching between checkout schemes.
+4. Disk space:
    Make sure that you have enough available disk space before starting.
    The source code, including full git history, requires about 3.5 GB.
    Build artifacts take anywhere between 5 GB to 70 GB, depending on the
    build settings.
-4. Time:
+5. Time:
    Depending on your machine and build settings,
    a from-scratch build can take a few minutes to several hours,
    so you might want to grab a beverage while you follow the instructions.