Documentation: convert uses of git-link macro to gitlink

There isn't and never was such a macro; all uses are typos.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/config.txt

@@ -223,14 +223,14 @@ showbranch.default::
 	See gitlink:git-show-branch[1].
 
 tar.umask::
-	By default, git-link:git-tar-tree[1] sets file and directories modes
+	By default, gitlink:git-tar-tree[1] sets file and directories modes
 	to 0666 or 0777. While this is both useful and acceptable for projects
 	such as the Linux Kernel, it might be excessive for other projects.
 	With this variable, it becomes possible to tell
-	git-link:git-tar-tree[1] to apply a specific umask to the modes above.
+	gitlink:git-tar-tree[1] to apply a specific umask to the modes above.
 	The special value "user" indicates that the user's current umask will
 	be used. This should be enough for most projects, as it will lead to
-	the same permissions as git-link:git-checkout[1] would use. The default
+	the same permissions as gitlink:git-checkout[1] would use. The default
 	value remains 0, which means world read-write.
 
 user.email::

Documentation/git-cvsimport.txt

@@ -116,7 +116,7 @@ file each time git-cvsimport is run.
 +
 It is not recommended to use this feature if you intend to
 export changes back to CVS again later with
-git-link[1]::git-cvsexportcommit.
+gitlink:git-cvsexportcommit[1].
 
 OUTPUT
 ------