title: find out when a git branch was created (not the first commit to that branch)
body: <p>how can I know when a git branch was created?</p>
  
  <p>i don't want to know when was the first commit to that branch.
  I want to find out when that branch was created.</p>
  
  <p>This is a script to reproduce a working example:</p>
  
  <pre><code>#! /bin/bash
  set -x
  set -e
  
  mkdir test
  cd test
  git init
  echo "hello" &gt;readme
  git add readme
  git commit -m "initial import"
  date
  
  sleep 5
  git checkout -b br1
  date                   # this is the date that I want to find out.
  
  sleep 5
  echo "hello_br1" &gt;readme
  git commit -a -m "hello_br1"
  date
  
  echo "hello_br1_b" &gt;readme
  git commit -a -m "hello_br1_b"
  
  git checkout master
  echo "hello_master" &gt;readme
  git commit -a -m "hello_master"
  
  git branch -a; 
  git log --all --graph --abbrev-commit --decorate --pretty=format:"%h - %an, %ad : %s" --date=iso
  </code></pre>
  
  <p>Executing this:</p>
  
  <pre><code>./test.sh 
  ++ set -e
  ++ mkdir test
  ++ cd test
  ++ git init
  Initialized empty Git repository in /test_git/test2/.git/
  ++ echo hello
  ++ git add readme
  ++ git commit -m 'initial import'
  [master (root-commit) 9b95944] initial import
   1 files changed, 1 insertions(+), 0 deletions(-)
   create mode 100644 readme
  ++ date
  Fri Aug 16 17:51:24 CEST 2013
  ++ sleep 5
  ++ git checkout -b br1
  Switched to a new branch 'br1'
  ++ date
  Fri Aug 16 17:51:29 CEST 2013
  ++ sleep 5
  ++ echo hello_br1
  ++ git commit -a -m hello_br1
  [br1 6c559cd] hello_br1
   1 files changed, 1 insertions(+), 1 deletions(-)
  ++ date
  Fri Aug 16 17:51:34 CEST 2013
  ++ echo hello_br1_b
  ++ git commit -a -m hello_br1_b
  [br1 5f0d8ab] hello_br1_b
   1 files changed, 1 insertions(+), 1 deletions(-)
  ++ git checkout master
  Switched to branch 'master'
  ++ echo hello_master
  ++ git commit -a -m hello_master
  [master 2ed092d] hello_master
   1 files changed, 1 insertions(+), 1 deletions(-)
  ++ git branch -a
    br1
  * master
  ++ git log --all --graph --abbrev-commit --decorate '--pretty=format:%h - %an, %ad : %s' --date=iso
  * 5f0d8ab - David Portabella, 2013-08-16 17:51:34 +0200 : hello_br1_b
  * 6c559cd - David Portabella, 2013-08-16 17:51:34 +0200 : hello_br1
  | * 2ed092d - David Portabella, 2013-08-16 17:51:34 +0200 : hello_master
  |/  
  * 9b95944 - David Portabella, 2013-08-16 17:51:24 +0200 : initial import
  </code></pre>
  
  <p>so, with git log, or git reflog, I can find out the date of the initial import (17:51:24) and the date of the first commit to the branch br1 (17:51:34).</p>
  
  <p>but I need to find out when the branch br1 was created (17:51:29).</p>
  
  <p>how to do that?</p>
  
  <p>(bonus question: and, does it have a hash? how to know who created that branch)</p>