Bump to dev version 0.6.0.dev0 (quantumlib#1404)

* Bump to dev version 0.6.0.dev0

* include developer release docs

dev_tools/how-to-cut-a-release.md

@@ -0,0 +1,46 @@
+# Releasing Qualtran
+
+The steps are
+
+ 1. Bump the version number to the desired release version
+ 2. Tag the release
+ 3. Follow the Python packaging guide to generate a distribution and upload it
+ 4. Bump the version number to the next "dev" version
+
+The packaging guide instructions can be found at:
+https://packaging.python.org/en/latest/tutorials/packaging-projects/#generating-distribution-archives
+
+## Set the version number
+
+Open a PR to edit `qualtran/_version.py` to change the version string to "x.y.z" (without any dev specifier), which
+is the desired version number.
+It should have previously been set to "x.y.z.dev0".
+The PR should be merged to the `main` branch and care should be taken not to merge any other PRs until
+the entire process is completed.
+Draft the release notes and circulate them for review.
+
+## Tag the repository
+
+Use GitHub "Releases" to tag the release with release notes. Tags for "x.y.0" minor releases should go on `main`.
+Patch releases (z > 0) should be tagged against a `vx.y` branch unless the patch immediately follows a minor release.
+
+Follow the convention for tag names. Include the "v" in the tag name. 
+
+## Package the release
+
+Make sure you're on `main` and have pulled the version-bump commit.
+It's recommended to carefully run `git clean -ndx` (change n to f to actually do it) to prepare
+a pristine repository state.
+Then, follow the guidance at 
+https://packaging.python.org/en/latest/tutorials/packaging-projects/#generating-distribution-archives.
+
+Modify the command to upload to the main pypi repository (rather than the test repository used for the tutorial).
+
+## Bump the version number to dev
+
+Edit `_version.py` again, and change the version number from "x.y.z" to "x.(y+1).0.dev0".
+
+## Communicate
+
+Send an email to [[email protected]](https://groups.google.com/g/qualtran-announce) announcing 
+the release. Congrats!

qualtran/_version.py

@@ -12,4 +12,4 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-__version__ = "0.5.0"
+__version__ = "0.6.0.dev0"