Add better tag support in the git branch segment.

fish_prompt.fish

@@ -52,11 +52,15 @@
 
 function __bobthefish_git_branch -S -d 'Get the current git branch (or commitish)'
   set -l ref (command git symbolic-ref HEAD ^/dev/null)
-  if [ $status -gt 0 ]
-    set -l branch (command git show-ref --head -s --abbrev | head -n1 ^/dev/null)
-    set ref "$__bobthefish_detached_glyph $branch"
-  end
-  echo $ref | sed "s#refs/heads/#$__bobthefish_branch_glyph #"
+    and echo $ref | sed "s#refs/heads/#$__bobthefish_branch_glyph #"
+    and return
+
+  set -l tag (command git describe --tags --exact-match ^/dev/null)
+    and echo "$__bobthefish_tag_glyph $tag"
+    and return
+
+  set -l branch (command git show-ref --head -s --abbrev | head -n1 ^/dev/null)
+  echo "$__bobthefish_detached_glyph $branch"
 end
 
 function __bobthefish_hg_branch -S -d 'Get the current hg branch'