use fish's man function for &keywordprg

This makes it possible to use K to view the man page for the fish
builtin under the cursor.

Author: dag

README.md

@@ -3,9 +3,9 @@ vim-fish
 
 This is an addon for Vim providing filetype support for [fish][] scripts.  In
 addition to the normal Vim features such as syntax highlighting, automatic
-indentation, reformatting and filetype detection, this addon includes support
-for the third-party addons [UltiSnips][], [Syntastic][], [endwise][] and
-[commentary][] when any of those are installed.
+indentation, reformatting, keyword lookup and filetype detection, this addon
+includes support for the third-party addons [UltiSnips][], [Syntastic][],
+[endwise][] and [commentary][] when any of those are installed.
 
 Bonus feature: if you use Vim with `funced` in fish, Vim will enter Insert mode
 at the end of the last line inside the function, after indenting it once if

bin/man.fish

@@ -0,0 +1 @@
+man $argv

ftplugin/fish.vim

@@ -2,6 +2,11 @@ setlocal commentstring=#%s
 setlocal iskeyword=@,48-57,-,_,.,/
 setlocal formatprg=fish_indent
 
+" Use the 'man' wrapper function in fish to include fish's man pages.
+" Have to use a script for this; 'fish -c man' would make the the man page an
+" argument to fish instead of man.
+execute 'setlocal keywordprg=fish\ '.expand('<sfile>:p:h:h').'/bin/man.fish'
+
 let b:endwise_addition = 'end'
 let b:endwise_words = 'begin,function,if,switch,while,for'
 let b:endwise_syngroups = 'fishKeyword,fishConditional,fishRepeat'