Documentation: Fix broken links

core-tutorial.txt, cvs-migration.txt, tutorial-2.txt:
	Fix broken links.
Signed-off-by: NDmitry V. Levin <ldv@altlinux.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/core-tutorial.txt

@@ -1620,7 +1620,7 @@ suggested in the previous section may be new to you. You do not
 have to worry. git supports "shared public repository" style of
 cooperation you are probably more familiar with as well.
 
-See link:cvs-migration.txt[git for CVS users] for the details.
+See link:cvs-migration.html[git for CVS users] for the details.
 
 Bundling your work together
 ---------------------------

Documentation/cvs-migration.txt

@@ -172,7 +172,7 @@ Advanced Shared Repository Management
 
 Git allows you to specify scripts called "hooks" to be run at certain
 points.  You can use these, for example, to send all commits to the shared
-repository to a mailing list.  See link:hooks.txt[Hooks used by git].
+repository to a mailing list.  See link:hooks.html[Hooks used by git].
 
 You can enforce finer grained permissions using update hooks.  See
 link:howto/update-hook-example.txt[Controlling access to branches using

Documentation/tutorial-2.txt

@@ -368,7 +368,7 @@ in the index file is identical to the one in the working directory.
 In addition to being the staging area for new commits, the index file
 is also populated from the object database when checking out a
 branch, and is used to hold the trees involved in a merge operation.
-See the link:core-tutorial.txt[core tutorial] and the relevant man
+See the link:core-tutorial.html[core tutorial] and the relevant man
 pages for details.
 
 What next?