documentation: add missing fullstops

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Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-check-ref-format.txt

@@ -48,7 +48,7 @@ Git imposes the following rules on how references are named:
 
 . They cannot begin or end with a slash `/` or contain multiple
   consecutive slashes (see the `--normalize` option below for an
-  exception to this rule)
+  exception to this rule).
 
 . They cannot end with a dot `.`.
 

Documentation/git-diff-tree.txt

@@ -34,7 +34,7 @@ include::diff-options.txt[]
 	matching one of the provided pathspecs.
 
 -r::
-	Recurse into sub-trees
+	Recurse into sub-trees.
 
 -t::
 	Show tree entry itself as well as subtrees.  Implies -r.

Documentation/git-help.txt

@@ -42,7 +42,7 @@ former is internally converted into the latter.
 
 To display the linkgit:git[1] man page, use `git help git`.
 
-This page can be displayed with 'git help help' or `git help --help`
+This page can be displayed with 'git help help' or `git help --help`.
 
 OPTIONS
 -------