switch from CLA to DCO

Signed-off-by: Ryan Richard <richardry@vmware.com>

.pre-commit-config.yaml

@@ -1,6 +1,8 @@
 # This is a configuration for https://pre-commit.com/.
 # On macOS, try `brew install pre-commit` and then run `pre-commit install`.
 exclude: '^(site|generated)/'
+default_install_hook_types: [ pre-commit, commit-msg ]
+default_stages: [ pre-commit ]
 repos:
 - repo: https://github.com/pre-commit/pre-commit-hooks
   rev: v4.5.0
@@ -24,3 +26,9 @@ repos:
     name: Validate copyright year
     entry: hack/check-copyright-year.sh
     language: script
+    stages: [ pre-commit ]
+  - id: check-signoff
+    name: Check for Signed-off-by
+    entry: 'grep -q "^Signed-off-by: "'
+    language: system
+    stages: [ commit-msg ]

CONTRIBUTING.md

@@ -62,14 +62,64 @@ guidelines in the issue and pull request templates.
 
 Please follow the procedure described in [SECURITY.md](SECURITY.md).
 
-## CLA
+## DCO Sign off
 
-We welcome contributions from everyone, but we can only accept them if you sign
-our Contributor License Agreement (CLA). If you would like to contribute and you
-have not signed it, our CLA-bot will walk you through the process when you open
-a Pull Request. For questions about the CLA process, see the
-[FAQ](https://cla.vmware.com/faq) or submit a question through the GitHub issue
-tracker.
+To ensure that contributors are only submitting work that they have rights to, we are requiring
+everyone to acknowledge this by signing their work.
+
+Since this signature indicates your rights to the contribution and
+certifies the statements below, it must contain your real name and
+email address. Various forms of noreply email address must not be used.
+
+Any copyright notices in this repository should specify the authors as
+"the Pinniped contributors".
+
+To sign your work, just add a line like this at the end of your commit message:
+
+```
+Signed-off-by: John Smith <jsmith@vmware.com>
+```
+
+This can easily be done with the `--signoff` option to `git commit`.
+
+By doing this you state that you can certify the following (from [https://developercertificate.org/]):
+
+```
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.
+```
 
 ## Learning about Pinniped