Add arcanist plugin

plugins/arcanist/arcanist.plugin.zsh

@@ -0,0 +1,17 @@
+arc_quick_diff () {
+  git checkout -b "$(echo $1 | sed 's/[^0-9a-zA-Z]/_/g' | cut -c -20)-$(date '+%y%m%dT%H-%M-%S')"
+  git commit -a -m "$1"
+  all_arguments="$*"
+  remaining_arguments=${all_arguments#*"$2"}
+  arc diff --verbatim --allow-untracked --reviewers $2 $remaining_arguments
+}
+
+
+arc_quick_update () {
+  git commit -a -m "$1"
+  arc diff --allow-untracked -m "$1"
+}
+
+
+alias quickdiff='arc_quick_diff'
+alias arcupdate='arc_quick_update'