add stable.txt

[ cherry-picked from cilium/cilium repository ]

Add `stable.txt`, a file in the master branch that always points to the
latest stable release of Cilium. This file can be used as a reference by
tools such as the Cilium CLI to get the latest stable release version.
This pattern and file is already applied to the Hubble CLI repository.

Ultimately, this new file will allow the Cilium CLI to always install
the latest version of Cilium, as initially planned[0], instead of the
version hardcoded in the CLI binary.

[0]: cilium/cilium-cli#121 (comment)

Co-authored-by: Joe Stringer <[email protected]>
Signed-off-by: Robin Hahling <[email protected]>
Signed-off-by: Joe Stringer <[email protected]>
Signed-off-by: Quentin Monnet <[email protected]>

internal/bump-readme.sh

@@ -13,10 +13,16 @@ PROJECTS_REGEX='s/.*projects\/\([0-9]\+\).*/\1/'
 ACTS_YAML=".github/cilium-actions.yml"
 REMOTE="$(get_remote)"
 
+latest_stable=""
 for release in $(grep "General Announcement" README.rst \
                  | sed 's/.*tree\/\(v'"$MAJ_REGEX"'\).*/\1/'); do
     latest=$(git describe --tags $REMOTE/$release \
              | sed 's/v//' | sed 's/\('"$MIN_REGEX"'\).*/\1/')
+    if [ -z "$latest_stable" ]; then
+        # the first release in the list is the latest stable
+        latest_stable=$latest
+        echo "v$latest_stable" > stable.txt
+    fi
     if grep -q -F $latest README.rst; then
         continue
     fi
@@ -39,5 +45,10 @@ for release in $(grep "General Announcement" README.rst \
     sed -i 's/\(projects\/\)'$old_proj'/\1'$new_proj'/g' $ACTS_YAML
 done
 
-git add README.rst $ACTS_YAML
-git commit -s -m "Update stable releases"
+git add README.rst stable.txt $ACTS_YAML
+if ! git diff-index --quiet HEAD -- README.rst stable.txt $ACTS_YAML; then
+    git commit -s -m "Update stable releases"
+    echo "README.rst and stable.txt updated, submit the PR now."
+else
+    echo "No new releases found."
+fi