Add README-repo.txt file

For the "readme" section on the repo web page.  Pandoc is used to
generate the HTML file.

src/MacVim/README-repo.txt

@@ -0,0 +1,28 @@
+### MacVim ###
+
+MacVim is a port of the text editor Vim to Mac OS X.  More information can be
+found on the [project webpage][gcode].  The file `src/MacVim/README` gives an
+overview of the MacVim source code.
+
+
+### Branches ###
+
+`master`
+:   MacVim and core Vim sources
+`vim`
+:   Core Vim sources pulled from the SVN repository with the latest runtime
+:   files from the Vim FTP included
+`stable`
+:   Used to build the Stable binary distribution
+`feat/core-text`
+:   Core Text renderer (fast with improved Unicode rendering, but has some
+:   display issues)
+`feat/input`
+:   Refactored input code (improved input manager support, e.g. Kotoeri
+:   shortcuts like Cmd-Shift-; work, etc.)
+
+_Note:_ Branches starting with `feat/` are experimental and will be rebased
+against master occasionally (other branches will not be rebased).
+
+
+[gcode]:    http://code.google.com/p/macvim/