added integral theme

themes/integral/fish_prompt.fish

+# name: Integral
+function _git_branch_name
+  echo (command git symbolic-ref HEAD ^/dev/null | sed -e 's|^refs/heads/||')
+end
+
+function _git_vs_upstream
+  set -l count (command git rev-list --count --left-right "origin/$argv"...HEAD ^/dev/null)
+  switch $count
+    case "" # no upstream
+      echo ''
+    case "0?0" # equal to upstream
+      echo ''
+    case "0??" # ahead of upstream
+      echo u+
+    case "??0" # behind upstream
+      echo u-
+    case '???'      # diverged from upstream
+      echo u+-
+    end
+end
+
+function _is_git_dirty
+  echo (command git status -s --ignore-submodules=dirty ^/dev/null)
+end
+
+function fish_prompt
+  set -l blue (set_color blue)
+  set -l yellow (set_color yellow)
+  set -l normal (set_color normal)
+  set -l green (set_color green)
+
+  set -l arrow "∫"
+  set -l cwd $blue(basename (prompt_pwd))
+
+  if [ (_git_branch_name) ]
+    set -l git_branch (_git_branch_name)
+    set -l git_vs_upstream (_git_vs_upstream $git_branch)
+
+    if [ (_is_git_dirty) ]
+      set git_info $yellow '('$git_branch "±" "$git_vs_upstream"')' $normal
+    else if [ (_git_vs_upstream $git_branch) ]
+      set git_info $yellow '('$git_branch "$git_vs_upstream"')' $normal
+    else
+      set git_info $green '('$git_branch')' $normal
+    end
+  end
+
+  echo -n -s $cwd "$git_info" $normal $arrow ' '
+end
+
+function fish_right_prompt
+  set -l dark_gray (set_color 222)
+  
+  echo -n -s $dark_gray ' ['(date +%H:%M:%S)'] '
+
+end

themes/integral/readme.md

+## integral
+
+A simple git upstream theme.
+
+#### Characteristics
+
+* Current branch
+* Dirty working directory
+* Working directory
+* Git upstream status
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