Fix grammar nits in documentation and in code comments.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/sha1_file.c b/sha1_file.c
index b0c2435..6583797 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -148,7 +148,7 @@
 
 /*
  * NOTE! This returns a statically allocated buffer, so you have to be
- * careful about using it. Do a "xstrdup()" if you need to save the
+ * careful about using it. Do an "xstrdup()" if you need to save the
  * filename.
  *
  * Also note that this returns the location for creating.  Reading