Merge branch 'jn/maint-1.6.3-check-ref-format-doc' into maint-1.6.4

* jn/maint-1.6.3-check-ref-format-doc:
  Documentation: describe check-ref-format --branch

Documentation/git-check-ref-format.txt

@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git check-ref-format' <refname>
-'git check-ref-format' [--branch] <branchname-shorthand>
+'git check-ref-format' --branch <branchname-shorthand>
 
 DESCRIPTION
 -----------
@@ -63,8 +63,11 @@ reference name expressions (see linkgit:git-rev-parse[1]):
 
 . at-open-brace `@{` is used as a notation to access a reflog entry.
 
-With the `--branch` option, it expands a branch name shorthand and
-prints the name of the branch the shorthand refers to.
+With the `--branch` option, it expands the ``previous branch syntax''
+`@{-n}`.  For example, `@{-1}` is a way to refer the last branch you
+were on.  This option should be used by porcelains to accept this
+syntax anywhere a branch name is expected, so they can act as if you
+typed the branch name.
 
 EXAMPLE
 -------