Add git support to fresh prompt theme

prompt_fresh_setup

@@ -1,8 +1,6 @@
-visible_length() {
-  echo $(( ${#${(S%%)1//(\%(KF1]|)\{*\}|\%[Bbkf])}} ))
-}
-
 prompt_fresh_setup() {
+  compile_git_prompt
+
   autoload -U add-zsh-hook
   add-zsh-hook precmd fresh_precmd
 
@@ -23,25 +21,151 @@ prompt_fresh_setup() {
 
   # TODO: RPS1
 
-  prompt_opts=(cr sp subst percent)
+  prompt_opts=(cr percent sp subst)
+}
+
+prompt_cleanup() {
+  if [ -f ~/.cache/zsh/git-prompt ]; then rm ~/.cache/zsh/git-prompt; fi
 }
 
 fresh_precmd() {
+  # First get the last commands exit code before doing anything
   local exit_code=$?
-  if [[ $exit_code -ne 0 ]]; then
-    local result="%{%B%F{1}%}$exit_code%{%f%b%}"
-  fi
 
+  # Construct the time and directory portions of the prompt
   local time_stamp="%{%F{244}%}%D{%H:%M:%S}%{%f%}"
   local directory="%{%F{37}%}%~%{%f%}"
 
-  # TODO: git status
+  # Check we are in a git repository
+  if `git rev-parse --git-dir > /dev/null 2>&1`; then
+    # Get git branch name & exit early if not found
+    local branch="`git symbolic-ref HEAD 2> /dev/null`"
+    if [ "" = "$branch" ]; then
+      local branch="`git rev-parse --abbrev-ref HEAD`"
+      if [ "HEAD" = "$branch" ]; then
+        local branch="`git rev-parse --short $branch`"
+      fi
+    fi
 
-  local line="$time_stamp $directory"
+    if [ "$branch" != "" ]; then
+      local branch=${branch#refs/heads/}
+      # Get the number of commits ahead/behind from the remote branch
+      local remote="`git config branch.$branch.remote 2> /dev/null`"
+      if [ "" != "remote" ]; then
+        local branches="refs/remotes/$remote/$branch...HEAD"
+        local nahead=`git rev-list --right-only $branches --count 2> /dev/null`
+        if [ "0" -ne "$nahead" ]; then local ahead="↑$nahead"; fi
+        local nbehind=`git rev-list --left-only $branches --count 2> /dev/null`
+        if [ "0" -ne "$nbehind" ]; then local behind="↓$nbehind"; fi
+      fi
 
-  local length=`visible_length "$line$result"`
+      # Construct the git prompt
+      local git="%{%F{66}%}$branch%{%f%}$ahead$behind "
 
-  print -P "$line${(l:COLUMNS - $length - 1:: :)}$result"
+      if [ -f ~/.cache/zsh/git-prompt ]; then
+        # Get the change counts from git-prompt
+        local counts=(`~/.cache/zsh/git-prompt`)
+
+        # Parse the results from git-prompt
+        if [ 0 -eq ${#counts[@]} ]; then # clean
+          local git="$git%{%B%F{2}%}✓%{%f%b%}";
+        else
+          if [ 0 != $counts[1] ]; then  # indexed
+            local git="$git%{%F{2}%}*$counts[1]%{%f%}"
+          fi
+          if [ 0 != $counts[2] ]; then  # modified
+            local git="$git%{%F{1}%}+$counts[2]%{%f%}";
+          fi
+          if [ 0 != $counts[3] ]; then  # deleted
+            local git="$git%{%F{1}%}-$counts[3]%{%f%}";
+          fi
+          if [ 0 != $counts[4] ]; then  # unmerged
+            local git="$git%{%B%F{1}%}×$counts[4]%{%f%b%}";
+          fi
+          if [ 0 != $counts[5] ]; then  # untracked
+            local git="$git%{%F{1}%}…%{%f%}";
+          fi
+        fi
+      fi
+    fi
+  fi
+
+  # Construct the prompt string
+  local line="$time_stamp $directory $git"
+
+  # Print the first line of the prompt
+  if [[ $exit_code -eq 0 ]]; then
+    print -P "$line"
+  else
+    # The last command failed, display its error code at the right
+    local result="%{%B%F{1}%}$exit_code%{%f%b%}"
+    local length=`visible_length "$line$result"`
+    print -P "$line${(l:COLUMNS - $length - 1:: :)}$result"
+  fi
+}
+
+visible_length() {
+  echo $(( ${#${(S%%)1//(\%(KF1]|)\{*\}|\%[Bbkf])}} ))
+}
+
+compile_git_prompt() {
+  # Compile a simple C executable which parses the output of `git status
+  # --procelain` to greatly decrease the time taken to render the prompt
+  if [ ! -d ~/.cache/zsh ]; then mkdir -p ~/.cache/zsh; fi
+  if [ ! -f ~/.cache/zsh/git-prompt ]; then
+    cc -x c -std=gnu99 -O3 -DNDEBUG -o ~/.cache/zsh/git-prompt - << EOF
+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+  FILE *file = popen("git status --porcelain", "r");
+  if (NULL == file) { return 0; }
+
+  char status[2048];
+  int indexed = 0, modified = 0, deleted = 0, untracked = 0, unmerged = 0;
+
+  while (NULL != fgets(status, sizeof(status) - 1, file)) {
+    char X = status[0];
+    char Y = status[1];
+
+    if (X == '?' && Y == '?') {
+      ++untracked;
+    } else if ((X == 'A' && (Y == 'A' || Y == 'U')) ||
+               (X == 'D' && (Y == 'D' || Y == 'U')) ||
+               (X == 'U' && (Y == 'A' || Y == 'D' || Y == 'D' || Y == 'U'))) {
+      ++unmerged;
+    } else {
+      switch (X) {
+      case ' ':
+        switch (Y) {
+          case 'M': ++modified; break;
+          case 'D': ++deleted; break;
+        } break;
+      case 'D': ++indexed;
+        switch (Y) {
+          case ' ': break;
+          case 'M': ++modified; break;
+        } break;
+      case 'M': case 'A': case 'R': case 'C': ++indexed;
+        switch (Y) {
+          case ' ': break;
+          case 'M': ++modified; break;
+          case 'D': ++deleted; break;
+        } break;
+      }
+    }
+  }
+
+  pclose(file);
+
+  if (indexed || modified || deleted || unmerged || untracked) {
+    printf("%d %d %d %d %d", indexed, modified, deleted, unmerged, untracked);
+  }
+
+  return 0;
+}
+EOF
+  fi
 }
 
 prompt_fresh_setup "$@"