Merge pull request #112 from dawikur/feature/git_prompt_tips

Add Tips section to README

README.md

@@ -239,6 +239,45 @@ or don't want to see. All options must be overridden in your **.zshrc** file.
 |`BULLETTRAIN_EXEC_TIME_BG`|`yellow`|Background color
 |`BULLETTRAIN_EXEC_TIME_FG`|`black`|Foreground color
 
+## Tips
+
+### BULLETTRAIN_GIT_PROMPT_CMD
+
+Allows you to specify custom git prompt command. This makes it possible to
+change:
+
+![Git_Prompt_Origin](./img/tips/git_prompt_origin.png)
+
+into:
+
+![Git_Prompt_Command](./img/tips/git_prompt_command.png)
+
+with:
+
+``` bash
+BULLETTRAIN_GIT_PROMPT_CMD=\${\$(git_prompt_info)//\\//\ \ }
+```
+
+Please note we need to delay variable expansion, so we have to escape all
+**weird** character - *$*, *\*, *\<space>*, etc.
+
+You can also use function to get more complex commands:
+
+``` bash
+BULLETTRAIN_GIT_PROMPT_CMD="\$(custom_git_prompt)"
+
+custom_git_prompt() {
+  prompt=$(git_prompt_info)
+  prompt=${prompt//\//\ \ }
+  prompt=${prompt//_/\ }
+  echo ${prompt}
+}
+```
+
+which gives:
+
+![Git_Prompt_Function](./img/tips/git_prompt_function.png)
+
 ## Contributors
 
 That project was originally a fork from