/* first, make sure you at least have the child branch */
git checkout feature/mychildbranch


/* ok, just show the branches.  make sure at least feature/mychildbranch exists  note the "*" below says "this is the branch i am on" */
git branch
    * feature/mychildbranch
      feature/myparentbranch


/* now checkout the parent branch...note the "switched" happens automatically with the checkout */    
git checkout feature/myparentbranch
    Switched to branch 'feature/myparentbranch'
    Your branch is up to date with 'origin/feature/myparentbranch'.

/* not pull, the pull will occur on the branch you are currently on, which should be feature/myparentbranch at this point */    
git pull
    remote: Enumerating objects: 69, done.
    remote: Counting objects: 100% (55/55), done.
    remote: Compressing objects: 100% (22/22), done.
    remote: Total 22 (delta 17), reused 0 (delta 0)
    Unpacking objects: 100% (22/22), done.
    From https://mygit.hub.com
       96ae0e9..6eb0a03  feature/myparentbranch -> origin/feature/myparentbranch
        * [new branch]      feature/blah blah blah (specific to my stuff only)
       xb99638..x86db6f  master                  -> origin/master
    Updating x6ae0e9..xeb0a03
    Fast-forward
     .../somefileone.txt | 30 ++++++++++++--------
     .../somefiletwo.txt       |  7 +++--
     .../somefilethree.txt  |  6 ++--
     X files changed, Y insertions(+), Z deletions(-)
     create mode 100644 somenewfileone.txt

/* do a git branch just to show that you're on feature/myparentbranch */    
git branch
  feature/mychildbranch
* feature/myparentbranch

/* ok, now (above) you have the latest-greatest feature/myparent, lets do a checkout on the child to switch to the child */    
git checkout feature/mychildbranch
Switched to branch 'feature/mychildbranch'
Your branch is up to date with 'origin/feature/mychildbranch'.

/* another sanity check, show you're on feature/mychildbranch */
git branch
* feature/mychildbranch
  feature/myparentbranch

/* finally, the magic.  do a merge from feature/myparentbranch (which you know is local and up to date because of the voodoo above */    
git merge feature/myparentbranch
Merge made by the 'recursive' strategy.
 .../somefileone.txt | 30 ++++++++++++--------
 .../somefiletwo.txt       |  7 +++--
 .../somefilethree.txt  |  6 ++--
 X files changed, Y insertions(+), Z deletions(-)
 create mode 100644 somenewfileone.txt