Git configuration

Nicer diffs (courtesy of Mo Zhou at Debian) and fewer keystrokes for maximum productivity:

[core]
  # $ cd /usr/share/doc/git/contrib/diff-highlight/
  # $ sudo make
  # $ cp diff-highlight ~/.local/bin/
  pager = ~/.local/bin/diff-highlight | less --tabs=4 -RFX
[alias]
  a = add
  aa = add --all
  ch = checkout
  chb = checkout -b
  c = commit
  cm = commit -m
  d = diff
  dw = diff --word-diff
  dd = diff --word-diff-regex=.
  ds = diff --staged
  dsw = diff --staged --word-diff
  dsd = diff --staged --word-diff-regex=.
  f = fetch
  l = log
  m = merge
  mn = merge --no-ff --no-commit
  p = push
  sh = show
  shw = show --word-diff
  shd = show --word-diff-regex=.
  shn = show --name-status
  shf = show --first-parent
  s = status