Implement diff-so-fancy script for use without Git

"diff-so-fancy" (1) has been designed to work within Git controlled
directories. To allow to use it to compare files that are not controlled
by Git the "--no-index" (2) option of "git-diff" has been used.

The script pipes the output to "less" using the options

* "-R, --RAW-CONTROL-CHARS" to only display ANSI "color" escape
  sequences in "raw" form
* "-F, --quit-if-one-screen" to automatically exit if the entire file
  can be displayed on the first screen.
* "-X, --no-init" to disable sending the termcap (de)initialization
  strings to the terminal to avoid unnecessary operations like clearing the screen.
* "-x2, --tabs=2" to use two tab stops.

References:

  * so-fancy/diff-so-fancy#220 (comment)
  (1) https://github.com/so-fancy/diff-so-fancy
  (2) https://git-scm.com/docs/git-diff#git-diff-emgitdiffem--no-index--options--ltpathgt823082

GH-61

snowblocks/bash/bin/dsf

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Copyright (c) 2016-2017 Arctic Ice Studio <development@arcticicestudio.com>
+# Copyright (c) 2016-2017 Sven Greb <code@svengreb.de>
+
+# Project:    igloo
+# Repository: https://github.com/arcticicestudio/igloo
+# License:    MIT
+
+set -euo pipefail
+
+# Allows to use "diff-so-fancy" to compare files that are not controlled by Git.
+# Under the hood it makes use of "git diff" by using the "no-index" option which allows to compare the given two
+# paths/files on the filesystem outside a working tree controlled by Git.
+#
+# @param $1 the path/files to compare
+# @param $2 the path/files to be compared
+# @see https://github.com/so-fancy/diff-so-fancy/issues/220#issuecomment-282530252
+dsf() {
+  if [ "$#" -eq 2 ]; then
+    git diff --no-index --color "$@" | diff-so-fancy | less -RFXx2
+  fi
+}
+
+dsf $@