fish_add_path: Be more informative in verbose mode

One issue with fish_add_path at the moment is that it is sometimes a bit too intransparent.

You'll try to add a path, but it won't appear - was that because it wasn't a directory,
or because it doesn't exist, or because it was already included?

If it isn't usable after, did fish_add_path not add it because of something or did something *else* remove it?

So we give more explanations - "skipping this because it's a file", "not setting anything because no paths are left to add", ...

share/functions/fish_add_path.fish

@@ -70,6 +70,8 @@ function fish_add_path --description "Add paths to the PATH"
             if set -q _flag_move; and not contains -- $p $newpaths
                 set -a indexes $ind
                 set -a newpaths $p
+            else if set -q _flag_verbose
+                printf (_ "Skipping already included path: %s\n") "$p"
             end
         else if not contains -- $p $newpaths
             # Without move, we only add it if it's not in.
@@ -99,6 +101,10 @@ function fish_add_path --description "Add paths to the PATH"
         and set $scope $var $newvar
         return 0
     else
+        if set -q _flag_verbose
+            # print a message in verbose mode
+            printf (_ "No paths to add, not setting anything.\n") "$p"
+        end
         return 1
     end
 end

tests/checks/fish_add_path.fish

@@ -25,6 +25,8 @@ function checkpath --on-variable PATH --on-variable fish_user_paths; echo CHECKP
 set PATH $PATH
 # CHECK: CHECKPATH: VARIABLE SET PATH
 fish_add_path -v $tmpdir/bin
+# CHECK: Skipping already included path: {{.*}}
+# CHECK: No paths to add, not setting anything.
 # Nothing happened, so the status failed.
 echo $status
 # CHECK: 1