Incorporated suggestions into git page and edit for more brevity.

The Advanced Rebasing section has been mostly rewritten to include
both a major suggestion from jyn and a general rewrite. Additional
thanks to camelid for some suggestions!

Author: JakobDegen

src/SUMMARY.md

@@ -31,7 +31,7 @@
 
 - [Introduction](./contributing.md)
 - [About the compiler team](./compiler-team.md)
-- [Using git](./git.md)
+- [Using Git](./git.md)
 - [Mastering @rustbot](./rustbot.md)
 - [Walkthrough: a typical contribution](./walkthrough.md)
 - [Bug Fix Procedure](./bug-fix-procedure.md)

src/git.md

@@ -1,29 +1,29 @@
-# Using git
+# Using Git
 
-The Rust project uses [git] to manage its source code. In order to
+The Rust project uses [Git] to manage its source code. In order to
 contribute, you'll need some familiarity with its features so that your changes
 can be incorporated into the compiler.
 
-[git]: https://git-scm.com
+[Git]: https://git-scm.com
 
 The goal of this page is to cover some of the more common questions and
-problems new contributors face. Although some git basics will be covered here,
+problems new contributors face. Although some Git basics will be covered here,
 if you  find that this is still a little too fast for you, it might make sense
-to first read some introductions to git, such as the Beginner and Getting
+to first read some introductions to Git, such as the Beginner and Getting
 started sections of [this tutorial from Atlassian][atlassian-git]. GitHub also
 provides [documentation] and [guides] for beginners, or you can consult the
-more in depth [book from git].
+more in depth [book from Git].
 
-[book from git]: https://git-scm.com/book/en/v2/
+[book from Git]: https://git-scm.com/book/en/v2/
 [atlassian-git]: https://www.atlassian.com/git/tutorials/what-is-version-control
 [documentation]: https://docs.github.com/en/github/getting-started-with-github/set-up-git
 [guides]: https://guides.github.com/introduction/git-handbook/
 
 ## Prequisites
 
-We'll assume that you've installed git, forked [rust-lang/rust], and cloned the
+We'll assume that you've installed Git, forked [rust-lang/rust], and cloned the
 forked repo to your PC. We'll use the command line interface to interact
-with git; there are also a number of GUIs and IDE integrations that can
+with Git; there are also a number of GUIs and IDE integrations that can
 generally do the same things.
 
 [rust-lang/rust]: https://github.com/rust-lang/rust
@@ -33,13 +33,13 @@ in your local repo. It may be helpful to also set up a remote for the official
 rust-lang/rust repo via
 
 ```sh
-git remote add rust https://github.com/rust-lang/rust.git
+git remote add upstream https://github.com/rust-lang/rust.git
 ```
 
 if you're using HTTPS, or
 
 ```sh
-git remote add rust [email protected]:rust-lang/rust.git
+git remote add upstream [email protected]:rust-lang/rust.git
 ```
 
 if you're using SSH.
@@ -51,7 +51,7 @@ and PRs:
 
  1. Ensure that you're making your changes on top of master:
  `git checkout master`.
- 2. Get the latest changes from the Rust repo: `git pull rust master`.
+ 2. Get the latest changes from the Rust repo: `git pull upstream master`.
  3. Make a new branch for your change: `git checkout -b issue-12345-fix`.
  4. Make some changes to the repo and test them.
  5. Stage your changes via `git add src/changed/file.rs src/another/change.rs`
@@ -60,7 +60,7 @@ and PRs:
  unintentionally commit changes that should not be committed, such as submodule
  updates. You can use `git status` to check if there are any files you forgot
  to stage.
- 6. Push your changes to your fork: `git push -u origin issue-12345-fix`.
+ 6. Push your changes to your fork: `git push --set-upstream origin issue-12345-fix`.
  7. [Open a PR][ghpullrequest] from your fork to rust-lang/rust's master branch.
 
 [ghpullrequest]: https://guides.github.com/activities/forking/#making-a-pull-request
@@ -82,19 +82,19 @@ to rust-lang/rust since then are in conflict with the changes you've made.
 
 When this happens, you need to resolve the conflicts before your changes can be
 merged. First, get a local copy of the conflicting changes: Checkout your local
-master branch with `git checkout master`, then `git pull rust master` to
+master branch with `git checkout master`, then `git pull upstream master` to
 update it with the most recent changes.
 
 ### Rebasing
 
-You're now ready to start the rebasing process. Check out the branch with your
+You're now ready to start the rebasing process. Checkout the branch with your
 changes and execute `git rebase master`.
 
 When you rebase a branch on master, all the changes on your branch are
-reapplied to the most recent version of master. In other words, git tries to
+reapplied to the most recent version of master. In other words, Git tries to
 pretend that the changes you made to the old version of master were instead
 made to the new version of master. During this process, you should expect to
-encounter at least one "rebase conflict." This happens when git's attempt to
+encounter at least one "rebase conflict." This happens when Git's attempt to
 reapply the changes fails because your changes conflicted with other changes
 that have been made. You can tell that this happened because you'll see
 lines in the output that look like
@@ -113,24 +113,24 @@ Your code
 >>>>>>> 8fbf656... Commit fixes 12345
 ```
 
-This represents the lines in the file that git could not figure out how to
+This represents the lines in the file that Git could not figure out how to
 rebase. The section between `<<<<<<< HEAD` and `=======` has the code from
 master, while the other side has your version of the code. You'll need to
 decide how to deal with the conflict. You may want to keep your changes,
 keep the changes on master, or combine the two.
 
-Generally, resovling the conflict consists of two steps: First, fix the
+Generally, resolving the conflict consists of two steps: First, fix the
 particular conflict. Edit the file to make the changes you want and remove the
 `<<<<<<<`, `=======` and `>>>>>>>` lines in the process. Second, check the
-surrounding code. If there was a conflict, its because someone else changed the
-same code you did. That means its likely there are some logical errors lying
-around too!
+surrounding code. If there was a conflict, its likely there are some logical
+errors lying around too! It's a good idea to run `x.py check` here to make sure
+there are no glaring errors.
 
 Once you're all done fixing the conflicts, you need to stage the files that had
 conflicts in them via `git add`. Afterwards, run `git rebase --continue` to let
-git know that you've resolved the conflicts and it should finish the rebase.
+Git know that you've resolved the conflicts and it should finish the rebase.
 Once the rebase has succeeded, you'll want to update the associated branch on
-your fork with `git push -f`.
+your fork with `git push --force-with-lease`.
 
 Note that `git push` will not work properly and say something like this:
 
@@ -143,32 +143,37 @@ hint: 'git pull ...') before pushing again.
 hint: See the 'Note about fast-forwards' in 'git push --help' for details.
 ```
 
-The advice this gives is incorrect! Because of the "no-merge" policy, running
-`git pull` will create a merge commit, defeating the point of your rebase. Use
-`git push -f` instead.
+The advice this gives is incorrect! Because of Rust's
+["no-merge" policy](#no-merge-policy) the merge commit created by `git pull`
+will not be allowed in the final PR, in addition to defeating the point of the
+rebase! Use `git push --force-with-lease` instead.
 
 ## Advanced Rebasing
 
-Sometimes, you may want to perform a more complicated rebase. There are two
-common scenarios that might call for this.
-
 If your branch contains multiple consecutive rewrites of the same code, or if
-the rebase conflicts are extremely severe, it is possible that just trying to
-reapply the changes you made on top of the updated code will be too much of a
-headache. In this case, you can use the interactive rebase feature via
-`git rebase -i master` to gain more control over the process. This allows you
-to choose to skip commits because they represent changes you no longer need,
-edit the commits that you do not skip, or change the order in which they are
-applied.
-
-The other common scenario is if you are asked to or want to "squash" multiple
-commits into each other. If you PR needs only a minor revision, a single commit
-at the end with message "fixup small issue" is usually unhelpful, and it is
-easier for everyone if you combine that commit with another that has a more
-meaningful commit message. Run `git rebase -i HEAD~2` to edit the last two
-commits so you can merge them together. By selecting the `-i` option, you give
-yourself the opportunity to edit the rebase, similarly to above. This way you
-can request to have the most recent commit squashed into its parent.
+the rebase conflicts are extremely severe, you can use
+`git rebase --interactive master` to gain more control over the process. This
+allows you to choose to skip commits, edit the commits that you do not skip,
+change the order in which they are applied, or "squash" them into each other.
+
+Alternatively, you can sacrifice the commit history like this:
+
+```
+# squash all the changes into one commit so you only have to worry about conflicts once
+git rebase -i $(git merge-base master)  # and squash all changes along the way
+git rebase master
+# fix all merge conflicts
+git rebase --continue
+```
+
+"Squashing" commits into each other causes them to be merged into a single
+commit. Both the upside and downside of this is that it simplifies the history.
+On the one hand, you lose track of the steps in which changes were made, but
+the history becomes easier to work with.
+
+You also may want to squash just the last few commits together, possibly
+because they only represent "fixups" and not real changes. For example,
+`git rebase --interactive HEAD~2` will allow you to edit the two commits only.
 
 ## No-Merge Policy