README.md: add hyperlinks on filenames

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

README.md

@@ -21,17 +21,17 @@ License version 2 (some parts of it are under different licenses,
 compatible with the GPLv2). It was originally written by Linus
 Torvalds with help of a group of hackers around the net.
-Please read the file INSTALL for installation instructions.
-See Documentation/gittutorial.txt to get started, then see
-Documentation/giteveryday.txt for a useful minimum set of commands, and
-Documentation/git-commandname.txt for documentation of each command.
+Please read the file [INSTALL][] for installation instructions.
+See [Documentation/gittutorial.txt][] to get started, then see
+[Documentation/giteveryday.txt][] for a useful minimum set of commands, and
+[Documentation/git-commandname.txt][] for documentation of each command.
 If git has been correctly installed, then the tutorial can also be
 read with "man gittutorial" or "git help tutorial", and the
 documentation of each command with "man git-commandname" or "git help
 commandname".
-CVS users may also want to read Documentation/gitcvs-migration.txt
+CVS users may also want to read [Documentation/gitcvs-migration.txt][]
 ("man gitcvs-migration" or "git help cvs-migration" if git is
 installed).
@@ -41,7 +41,7 @@ including full documentation and Git related tools.
 The user discussion and development of Git take place on the Git
 mailing list -- everyone is welcome to post bug reports, feature
 requests, comments and patches to git@vger.kernel.org (read
-Documentation/SubmittingPatches for instructions on patch submission).
+[Documentation/SubmittingPatches][] for instructions on patch submission).
 To subscribe to the list, send an email with just "subscribe git" in
 the body to majordomo@vger.kernel.org. The mailing list archives are
 available at http://news.gmane.org/gmane.comp.version-control.git/,
@@ -51,3 +51,10 @@ The maintainer frequently sends the "What's cooking" reports that
 list the current status of various development topics to the mailing
 list.  The discussion following them give a good reference for
 project status, development direction and remaining tasks.
+
+[INSTALL]: INSTALL
+[Documentation/gittutorial.txt]: Documentation/gittutorial.txt
+[Documentation/giteveryday.txt]: Documentation/giteveryday.txt
+[Documentation/git-commandname.txt]: Documentation/git-commandname.txt
+[Documentation/gitcvs-migration.txt]: Documentation/gitcvs-migration.txt
+[Documentation/SubmittingPatches]: Documentation/SubmittingPatches