[bobthefish] Add ☿ (mercury) glyph to hg prompt

This makes it easier (possible?) to distinguish between hg and git repos at a glance.

fish_prompt.fish

@@ -31,6 +31,7 @@ set __bobthefish_detached_glyph          \u27A6
 set __bobthefish_nonzero_exit_glyph      '! '
 set __bobthefish_superuser_glyph         '$ '
 set __bobthefish_bg_job_glyph            '% '
+set __bobthefish_hg_glyph                \u263F
 
 # Python glyphs
 set __bobthefish_superscript_glyph       \u00B9 \u00B2 \u00B3
@@ -249,6 +250,9 @@ function __bobthefish_prompt_hg -d 'Display the actual hg state'
 
   __bobthefish_path_segment (__bobthefish_project_dir_hg)
 
+  __bobthefish_start_segment $flag_bg $flag_fg
+  echo -n -s $__bobthefish_hg_glyph ' '
+
   __bobthefish_start_segment $flag_bg $flag_fg
   set_color $flag_fg --bold
   echo -n -s (__bobthefish_hg_branch) $flags ' '