exa: install man page and shell completions

pkgs/tools/misc/exa/default.nix

@@ -23,6 +23,20 @@ buildRustPackage rec {
     libiconv darwin.apple_sdk.frameworks.Security ]
   ;
 
+  postInstall = ''
+    mkdir -p $out/share/man/man1
+    cp contrib/man/exa.1 $out/share/man/man1/
+
+    mkdir -p $out/share/bash-completion/completions
+    cp contrib/completions.bash $out/share/bash-completion/completions/exa
+
+    mkdir -p $out/share/fish/vendor_completions.d
+    cp contrib/completions.fish $out/share/fish/vendor_completions.d/exa.fish
+
+    mkdir -p $out/share/zsh/site-functions
+    cp contrib/completions.zsh $out/share/zsh/site-functions/_exa
+  '';
+
   # Some tests fail, but Travis ensures a proper build
   doCheck = false;