Add branch plugin

plugins/branch/README.md

+# Branch
+
+Displays the current Git or Mercurial branch fast.
+
+## Speed test
+
+### Mercurial
+
+```shell
+$ time hg branch
+0.11s user 0.14s system 70% cpu 0.355 total
+```
+
+### Branch plugin
+
+```shell
+$ time sh /tmp/branch_prompt_info.sh
+0.01s user 0.01s system 81% cpu 0.018 total
+```
+
+## Usage
+
+Edit your theme file (eg.: `~/.oh-my-zsh/theme/robbyrussell.zsh-theme`) 
+adding `$(branch_prompt_info)` in your prompt like this:
+
+```diff
+- PROMPT='${ret_status}%{$fg_bold[green]%}%p %{$fg[cyan]%}%c %{$fg_bold[blue]%}$(git_prompt_info)%{$fg_bold[blue]%} % %{$reset_color%}'
++ PROMPT='${ret_status}%{$fg_bold[green]%}%p %{$fg[cyan]%}%c %{$fg_bold[blue]%}$(git_prompt_info)$(branch_prompt_info)%{$fg_bold[blue]%} % %{$reset_color%}'
+```
+
+## Maintainer
+
+Victor Torres (<vpaivatorres@gmail.com>)

plugins/branch/branch.plugin.zsh

+# Branch: displays the current Git or Mercurial branch fast.
+# Victor Torres <vpaivatorres@gmail.com>
+# Oct 2, 2015
+
+function branch_prompt_info() {
+  # Defines path as current directory
+  path=$(pwd)
+  # While current path is not root path
+  while [ $path != '/' ];
+  do
+    # Git repository
+    if [ -d ${path}/.git ];
+    then
+      echo '±' $(/bin/cat ${path}/.git/HEAD | /usr/bin/cut -d / -f 3-)
+      return;
+    fi
+    # Mercurial repository
+    if [ -d ${path}/.hg ];
+    then
+      echo '☿' $(/bin/cat ${path}/.hg/branch)
+      return;
+    fi
+    # Defines path as parent directory and keeps looking for :)
+    path=$(/usr/bin/dirname $path)
+  done
+}