Git Merge Squash

gistfile1.txt

# Commit any working changes on branch "mybranchname", then...
git checkout master
git checkout -b mybranchname_temp
git merge --squash mybranchname
git commit -am "Message describing all squashed commits"
git branch -m mybranchname mybranchname_unsquashed
git branch -m mybranchname

# Optional cleanup:
git branch -D mybranchname_unsquashed

# If squashing already-pushed commits...
git push -f