Add unamend alias to help reversing an amend

* `unamend` applies the diff from a previous `commit --amend` to the
working tree to make it easy to undo an accidental amend.
* Removed `last` alias, use `checkout -` instead
* Rename `name` alias to `refname` to be less ambiguous

config

@@ -5,6 +5,11 @@
 	unstage = reset -q HEAD --
 
 	amend = commit --amend
+	unamend = !git diff $(git reflog -2 | \
+		awk \"{print \\$1}\" | \
+		sed -e ':a' -e 'N' -e '$!ba' -e 's/\\n/../g') | \
+		git apply - 2> /dev/null || \
+			echo \"error: last commit was not amended\"
 	fixup = commit --fixup
 	squash = commit --squash
 	prepare = rebase -i --fork-point
@@ -12,11 +17,10 @@
 	list = branch
 	create = checkout -b
 	delete = branch -D
-	name = rev-parse --abbrev-ref HEAD
-	last = !sh -c 'git reflog | grep \" checkout: moving from\" | head -n 1 | awk \"{ print \\$6 }\"'
+	refname = rev-parse --abbrev-ref HEAD
 
-	publish = !git push -u origin `git name`
-	unpublish = !git push -u origin :`git name`
+	publish = !git push -u origin `git refname`
+	unpublish = !git push -u origin :`git refname`
 	force = push --force-with-lease
 
 	changes = !sh -c 'git log --oneline $1..' --