__fish_config_interactive: Prefer python3

Also includes the CHANGELOG.

CHANGELOG.md

@@ -17,6 +17,7 @@
 - Command substitutions now have access to the terminal, allowing tools like `fzf` to work in them (#1362, #3922).
 - `bg`s argument parsing has been reworked. It now fails for invalid arguments but allows non-existent jobs (#3909).
 - fish will now reset $USER if the uid is 0. This is to workaround some su implementations that pass along $USER when switching to root (#3944).
+- Our python-using functions now pick any python version (preferring python3), making dependencies on a specific python version unnecessary (#3970).
 
 ---
 

share/functions/__fish_config_interactive.fish

@@ -122,12 +122,12 @@ function __fish_config_interactive -d "Initializations that should be performed
             # Hence we'll call python directly.
             # c_m_p.py should work with any python version.
             set -l update_args -B $__fish_datadir/tools/create_manpage_completions.py --manpath --cleanup-in '~/.config/fish/completions' --cleanup-in '~/.config/fish/generated_completions'
-            if command -qs python
-                python $update_args >/dev/null ^/dev/null &
+            if command -qs python3
+                python3 $update_args >/dev/null ^/dev/null &
             else if command -qs python2
                 python2 $update_args >/dev/null ^/dev/null &
-            else if command -qs python3
-                python3 $update_args >/dev/null ^/dev/null &
+            else if command -qs python
+                python $update_args >/dev/null ^/dev/null &
             end
         end
     end