Prepare release Prepare release v0.1.3
Prepare release Prepare release v0.1.3

Changes since v0.1.2
- Git-subproject no longer invokes `git merge --squash -s subtree2`, but
  uses the same shared merge implementation as the subtree2 merge
  strategy (this is an internal code change, that might improve
  performance, but does not affect externally visible behavior).

episource/git-merge-subtree2