docs: cherry-pick process (#26109)

Signed-off-by: Michael Crenshaw <350466+crenshaw-dev@users.noreply.github.com>

docs/developer-guide/backporting-fixes.md

@@ -0,0 +1,50 @@
+# Backporting Fixes
+
+After [submitting your PR](submit-your-pr.md) and getting it merged, you might want to backport it to previous releases.
+The prerequisites for backporting are:
+
+* Your PR is already merged into the `master` branch
+* The changes are a bugfix
+* The changes are non-breaking
+* The backports are to [actively supported releases](https://github.com/argoproj/argo-cd/security/policy#supported-versions)
+
+## Automated Process
+
+Adding a `cherry-pick/x.y` label to your PR (where `x.y` is the version you want to backport to e.g. `3.1`) will 
+trigger the cherry pick workflow to open a PR against the targeted release branch. Anyone with 
+[Argoproj membership](https://github.com/argoproj/argoproj/blob/main/community/membership.md) can add the label, but an
+Approver must merge the backport PR. If you cannot add the label yourself, ask the person who merged the PR to do it for
+you.
+
+## Manual Process
+
+Sometimes the automation fails, generally because the cherry-pick involves merge conflicts. In that case, you can
+manually create the backport PR. The process generally goes like this:
+
+```shell
+git checkout release-x.y
+git pull origin release-x.y
+git checkout -b backport-my-fix-to-x.y
+git cherry-pick <commit hash of your bugfix's squash commit in master>
+# Resolve any merge conflicts
+git commit
+git push <your fork> backport-my-fix-to-x.y
+# Open a PR against release-x.y
+```
+
+Then repeat for the other release branches you want to backport to. Sometimes it's easier to cherry-pick the commit with
+resolved conflicts from the release branch after you've resolved them for the first backport rather than repeatedly
+resolving the same conflicts from the master branch for each backport. For example, after doing the steps above, do:
+
+```shell
+git rev-parse HEAD
+# Note the commit hash
+git checkout release-x.<y-1>
+git pull origin release-x.<y-1>
+git checkout -b backport-my-fix-to-x.<y-1>
+git cherry-pick <commit hash from previous backport>
+# Resolve any merge conflicts
+git commit
+git push <your fork> backport-my-fix-to-x.<y-1>
+# Open a PR against release-x.<y-1>
+```

mkdocs.yml

@@ -213,6 +213,7 @@ nav:
   - Development Environment: developer-guide/development-environment.md
   - Development Cycle: developer-guide/development-cycle.md
   - Submit Your PR: developer-guide/submit-your-pr.md
+  - Backport Your Fix: developer-guide/backporting-fixes.md
   - Architecture:
     - developer-guide/architecture/authz-authn.md
     - developer-guide/architecture/components.md