enhancement with section header char for locating and control options about the ruler

[charlie-wong]

• add section header char, thus the section can be located
  • make diff-so-fancy works together with ov with more pertty output
  • add two options, -use-sc DIFF for customization, -N to reset/clean it
• add options to control the ruler type
  By default, top/bottom ruler is showing with unicode line-drawing chars.
  And if a ruler is marked to hiding, by default it will be replaced by newline.
  • -U mark top ruler to hiding, and -u make top ruler to showing
  • -D mark bottom ruler to hiding, and -d make bottom ruler to showing
  • -X mark showing ruler to be replaced with newline
  • -x mark hiding ruler to be replaced with newline

More examples and details can be found in README.md

[charlie-wong]

Usage demo with https://github.com/noborus/ov

# The git configuration to use with this demo
[pager]
  show = "diff-so-fancy | ov -F --header 3"
  log  = "ov -F --section-delimiter '^commit' --section-header-num 3"
  diff = "diff-so-fancy | ov -F --section-delimiter '^◯' --section-header-num 1"

[color "diff"]
  context    = 243           # gray
  meta       = yellow   bold
  commit     = yellow   bold
  frag       = 205   reverse # pink
  func       = cyan  reverse
  old        = red      bold
  new        = green    bold
  whitespace = red  reverse

[color "diff-highlight"]
  oldNormal    = red    bold
  oldHighlight = blue   reverse
  newNormal    = green  bold
  newHighlight = blue   reverse