fix: use string check to determine if filename is a fish file; fix #459

Bug was introduced in 7850f78e8a.

When removing a file don't use `functions -q $filename` as a loose
check for a .fish file. Use a string match instead.

`functions -q $filename` will cause the function defined in the file
to be autoloaded (if it wasn't already) which can cause trouble with
some "dubious" packages that run arbitrary code in function files.

fisher.fish

@@ -324,16 +324,13 @@ function _fisher_pkg_uninstall -a pkg
         set -l filename (echo "$target" | command sed 's|.fish||')
         switch $source
             case $pkg/conf.d\*
-                if test "$filename.fish" = "$target"
+                test "$filename.fish" = "$target"; and emit "$filename"_uninstall
-                    emit "$filename"_uninstall
-                end
                 set target conf.d/$target
             case $pkg/completions\*
-                if functions -q "$filename"
+                test "$filename.fish" = "$target"; and complete -ec $filename
-                    complete -ec $filename
-                end
                 set target completions/$target
             case $pkg/{,functions}\*
+                test "$filename.fish" = "$target"; and functions -e $filename
                 switch $target
                     case uninstall.fish
                         source $source
@@ -343,9 +340,6 @@ function _fisher_pkg_uninstall -a pkg
                     case \*
                         set target functions/$target
                 end
-                if functions -q "$filename"
-                    functions -e $filename
-                end
         end
         command rm -f $fisher_path/$target
     end