fish_git_prompt: Add a way to use the informative chars

$__fish_git_prompt_use_informative_chars will use the informative
chars without requiring informative mode (which is really frickin'
slow!).

See #5726.

[ci skip]

CHANGELOG.md

@@ -56,6 +56,7 @@
   - `bosh`
   - `vagrant`
 - The git prompt in informative mode now shows the number of stashes if enabled.
+- The git prompt now has an option ($__fish_git_prompt_use_informative_chars) to use the (more modern) informative characters without enabling informative mode.
 - The nextd and prevd functions no longer print "Hit end of history", instead using a BEL.
 - If fish_mode_prompt exists, vi-mode will only execute it on mode-switch instead of the entire prompt. This should make it much more responsive with slow prompts (#5783).
 - The path-component bindings (like ctrl-w) now also stop at ":" and "@" because those are used to denote user and host in ssh-likes (#5841).

share/functions/fish_git_prompt.fish

@@ -689,7 +689,9 @@ function __fish_git_prompt_set_char
     end
 
     if set -q argv[3]
-        and set -q __fish_git_prompt_show_informative_status
+        and begin set -q __fish_git_prompt_show_informative_status
+            or set -q __fish_git_prompt_use_informative_chars
+        end
         set char $argv[3]
     end
 
@@ -792,7 +794,7 @@ function __fish_git_prompt_validate_colors --description "fish_git_prompt helper
 end
 
 set -l varargs
-for var in repaint describe_style show_informative_status showdirtystate showstashstate showuntrackedfiles showupstream
+for var in repaint describe_style show_informative_status use_informative_chars showdirtystate showstashstate showuntrackedfiles showupstream
     set -a varargs --on-variable __fish_git_prompt_$var
 end
 function __fish_git_prompt_repaint $varargs --description "Event handler, repaints prompt when functionality changes"

sphinx_doc_src/cmds/fish_git_prompt.rst

@@ -50,7 +50,7 @@ There are numerous customization options, which can be controlled with git optio
 
 - ``$__fish_git_prompt_showcolorhints`` can be set to enable coloring for the branch name and status symbols.
 
-A number of variables set characters and color used as indicators. Many of these have a different default if used with informative status enabled. The usual default is given first, then the informative default (if it is different). If no default for the colors is given, they default to ``$__fish_git_prompt_color``.
+A number of variables set characters and color used as indicators. Many of these have a different default if used with informative status enabled, or ``$__fish_git_prompt_use_informative_chars`` set. The usual default is given first, then the informative default (if it is different). If no default for the colors is given, they default to ``$__fish_git_prompt_color``.
 
 - ``$__fish_git_prompt_char_stateseparator`` (' ', `|`)
 - ``$__fish_git_prompt_color`` ('')