arcanist: add functions which allow copy-pasting of URLS (#8688)

Co-authored-by: Marc Cornellà <marc.cornella@live.com>

plugins/arcanist/arcanist.plugin.zsh

@@ -13,10 +13,25 @@ alias ardc='arc diff --create'
 alias ardnu='arc diff --nounit'
 alias ardnupc='arc diff --nounit --plan-changes'
 alias ardpc='arc diff --plan-changes'
+alias ardp='arc diff --preview' # creates a new diff in the phab interface
 
 alias are='arc export'
 alias arh='arc help'
 alias arl='arc land'
 alias arli='arc lint'
 alias arls='arc list'
-alias arpa='arc patch'
+
+#
+# Functions
+# (sorted alphabetically)
+#
+
+ardu() {
+  # Both `ardu https://arcanist-url.com/<REVISION>`, and `ardu <REVISION>` work.
+  arc diff --update "${1:t}"
+}
+
+arpa() {
+  # Both `arpa https://arcanist-url.com/<REVISION>`, and `arpa <REVISION>` work.
+  arc patch "${1:t}"
+}