Add Clean Out All Local Branches as a git til.

git/clean-out-all-local-branches.md

@@ -0,0 +1,17 @@
+# Clean Out All Local Branches
+
+Sometimes a project can get to a point where there are so many local
+branches that deleting them one by one is too tedious. This one-liner can
+help:
+
+```
+$ git branch --merged master | grep -v master | xargs git branch -d
+```
+
+This won't delete branches that are unmerged which saves you from doing
+something stupid, but can be annoying if you know what you are doing. If you
+are sure you want to wipe everything, just use `-D` like so:
+
+```
+$ git branch --merged master | grep -v master | xargs git branch -D
+```