Documentation: the name of the system is 'Git', not 'git'

Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-mktag.txt b/Documentation/git-mktag.txt
index 65e167a..3ca158b 100644
--- a/Documentation/git-mktag.txt
+++ b/Documentation/git-mktag.txt
@@ -28,9 +28,9 @@
   tagger <tagger>
 
 followed by some 'optional' free-form message (some tags created
-by older git may not have `tagger` line).  The message, when
+by older Git may not have `tagger` line).  The message, when
 exists, is separated by a blank line from the header.  The
-message part may contain a signature that git itself doesn't
+message part may contain a signature that Git itself doesn't
 care about, but that can be verified with gpg.
 
 GIT