git: Add difftastic syntax diffing

If difft command is installed we can git diff on syntactic changes only
using `gdy` (or `gdys` for staged) which will spit out a (treesitter)
syntax-aware side by side comparison.
Really nice for refactoring diffs.

git/.config/git/config

@@ -6,6 +6,8 @@
   defaultBranch = main
 [core]
   pager = delta
+[pager]
+  difftool      = true
 [interactive]
   diffFilter = delta --color-only
 [merge]
@@ -23,6 +25,7 @@
   pushall       = "!git remote | xargs -I R git push R"   # push to all connected remotes
   fetchall      = "!git remote | xargs -I R git fetch R"  # fetch from all connected remotes
   diffword      = "!git diff --word-diff=color --word-diff-regex='[0-9A-Za-z_]+'"  # word-wise diff, good for prose
+  diffsyn       = "!git difftool --tool difftastic" # add syntax-driven diff using treesitter
 [commit]
   gpgsign       = true                                                 # sign commits as me
   verbose       = true                                                 # Always show diff when preparing commit message
@@ -32,6 +35,10 @@
   rebase        = true                                                 # always rebase on pulling, obviates merge commits
 [diff]
   colorMoved    = zebra                                                # also color stuff that has simply been moved, in a classy zebra-color
+[difftool]
+  prompt        = false
+[difftool "difftastic"]
+    cmd         = difft "$LOCAL" "$REMOTE"
 [color.diff]
   meta          = "9"
   frag          = "magenta bold"

git/.config/sh/alias.d/git.sh

@@ -38,8 +38,13 @@ alias gdds='git diffword --staged'
 
 alias gi='git ignore'
 
+# syntax-based diff
+if exist difft; then
+    alias gdy='git diffsyn'
+    alias gdys='git diffsyn --staged'
+fi
 # show last committed content
-alias gll='git last'
+alias gdl='git last'
 # show quick log overview
 alias glg='git log --oneline --decorate --graph'
 alias glgd="git log --graph --pretty=format:'%C(auto)%h%Creset %C(cyan)%ar%Creset%C(auto)%d%Creset %s'"