doc: git-checkout: clarify restoring files section

- Split up the forms `git checkout file.txt` and
  `git checkout main file.txt` to match what's given in the SYNOPSIS
- Remove `-f` from the SYNOPSIS for the second form, since according to
  this man page it is not relevant in that context
- Many Git users do not know what a "tree-ish" is. Clarify by using an
  example of each case, and by saying "commit or tree" in the text
  instead of "<tree-ish>"
- Many Git users do not know what the "index" is. Instead say "stage the
  file's contents" where appropriate, since Git often uses "stage" as a
  verb to mean the same thing as "add to the index" and it's a more
  familiar term.
- Use "Discard unstaged changes" instead of "checking out paths from
  the index" where relevant

Signed-off-by: Julia Evans <[email protected]>

Author: jvns

Documentation/git-checkout.adoc

@@ -12,8 +12,8 @@ git checkout [-q] [-f] [-m] [<branch>]
 git checkout [-q] [-f] [-m] --detach [<branch>]
 git checkout [-q] [-f] [-m] [--detach] <commit>
 git checkout [-q] [-f] [-m] [[-b|-B|--orphan] <new-branch>] [<start-point>]
-git checkout [-f] <tree-ish> [--] <pathspec>...
-git checkout [-f] <tree-ish> --pathspec-from-file=<file> [--pathspec-file-nul]
+git checkout <tree-ish> [--] <pathspec>...
+git checkout <tree-ish> --pathspec-from-file=<file> [--pathspec-file-nul]
 git checkout [-f|--ours|--theirs|-m|--conflict=<style>] [--] <pathspec>...
 git checkout [-f|--ours|--theirs|-m|--conflict=<style>] --pathspec-from-file=<file> [--pathspec-file-nul]
 git checkout (-p|--patch) [<tree-ish>] [--] [<pathspec>...]
@@ -75,25 +75,36 @@ that is, the branch will not be created or modified unless
 +
 Omitting _<branch>_ detaches `HEAD` at the tip of the current branch.
 
-`git checkout [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] [--] <pathspec>...`::
-`git checkout [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] --pathspec-from-file=<file> [--pathspec-file-nul]`::
+`git checkout <tree-ish> [--] <pathspec>...`::
+`git checkout <tree-ish> --pathspec-from-file=<file> [--pathspec-file-nul]`::
 
-	Overwrite the contents of the files that match the pathspec.
-	When the _<tree-ish>_ (most often a commit) is not given,
-	overwrite working tree with the contents in the index.
-	When the _<tree-ish>_ is given, overwrite both the index and
-	the working tree with the contents at the _<tree-ish>_.
+	Replace the specified files and/or directories with the version from
+	the given commit or tree.
 +
-The index may contain unmerged entries because of a previous failed merge.
-By default, if you try to check out such an entry from the index, the
-checkout operation will fail and nothing will be checked out.
-Using `-f` will ignore these unmerged entries.  The contents from a
-specific side of the merge can be checked out of the index by
-using `--ours` or `--theirs`.  With `-m`, changes made to the working tree
-file can be discarded to re-create the original conflicted merge result.
+For example, `git checkout main file.txt` will restore the version
+of `file.txt` from `main`. This overwrites the file in the working
+directory and stages the file's contents.
 
+`git checkout [-f|--ours|--theirs|-m|--conflict=<style>] <pathspec>...`::
+`git checkout [-f|--ours|--theirs|-m|--conflict=<style>] --pathspec-from-file=<file> [--pathspec-file-nul]`::
+
+	Replace the specified files and/or directories with the latest
+	committed or staged version.
++
+This overwrites the file(s) you specify with either the staged version
+or the version from the current commit if there is no staged version.
+For example, if you've been editing `file.txt` and you want to discard
+your changes to it, you can run `git checkout file.txt` to replace it
+with the latest committed version.
++
+This will fail if the file has a merge conflict and you haven't yet run
+`git add file.txt` (or something equivalent) to mark it as resolved.
+You can use `-f` to ignore the unmerged files instead of failing, use
+`--ours` or `--theirs` to replace them with the version from a specific
+side of the merge, or use `-m` to replace them with the original
+conflicted merge result.
 `git checkout (-p|--patch) [<tree-ish>] [--] [<pathspec>...]`::
-	This is similar to the previous mode, but lets you use the
+	This is similar to the previous two modes, but lets you use the
 	interactive interface to show the "diff" output and choose which
 	hunks to use in the result.  See below for the description of
 	`--patch` option.