CI: build: add support for external toolchains from stable branch

Add support to use external toolchains from stable branch if we are
testing commit targeting stable openwrt branch in kernel and packages
workflow.

With pr the target branch is parsed and the right toolchain is used.

To use the stable toolchain for local testing the branch needs to have
the prefix openwrt-[0-9][0-9].[0-9][0-9]- (example openwrt-21.02-fixup)

Signed-off-by: Christian Marangi <[email protected]>

.github/workflows/build.yml

@@ -145,13 +145,38 @@ jobs:
         if: inputs.build_toolchain == false
         working-directory: openwrt
         run: |
-          TOOLCHAIN_STRING="$(curl "https://downloads.cdn.openwrt.org/snapshots/targets/${{ env.TARGET }}/${{ env.SUBTARGET }}/sha256sums" \
+          TOOLCHAIN_PATH=snapshots
+
+          if [ -n "${{ github.base_ref }}" ]; then
+            if echo "${{ github.base_ref }}" | grep -q -E 'openwrt-[0-9][0-9]\.[0-9][0-9]'; then
+              major_ver="$(echo ${{ github.base_ref }} | sed 's/openwrt-/v/')"
+            fi
+          elif [ "${{ github.ref_type }}" = "branch" ]; then
+            if echo "${{ github.ref_name }}" | grep -q -E 'openwrt-[0-9][0-9]\.[0-9][0-9]-'; then
+              major_ver="$(echo ${{ github.ref_name }} | sed 's/openwrt-\([0-9][0-9]\.[0-9][0-9]\)-.*/v\1/')"
+            fi
+          elif [ "${{ github.ref_type }}" = "tag" ]; then
+            if echo "${{ github.ref_name }}" | grep -q -E 'v[0-9][0-9]\.[0-9][0-9]\..+'; then
+              major_ver="$(sed 's/\(v[0-9][0-9]\.[0-9][0-9]\)\..\+/\1/')"
+            fi
+          fi
+
+          if [ -n "$major_ver" ]; then
+            git fetch --tags
+            latest_tag="$(git tag --sort=-creatordate -l $major_ver* | head -n1)"
+            if [ -n "$latest_tag" ]; then
+              TOOLCHAIN_PATH=releases/$(echo $latest_tag | sed 's/^v//')
+            fi
+          fi
+
+          TOOLCHAIN_STRING="$(curl "https://downloads.cdn.openwrt.org/$TOOLCHAIN_PATH/targets/${{ env.TARGET }}/${{ env.SUBTARGET }}/sha256sums" \
             | grep ".*openwrt-toolchain.*tar.xz")"
           TOOLCHAIN_FILE=$(echo "$TOOLCHAIN_STRING" | sed -n -e 's/.*\(openwrt-toolchain.*\).tar.xz/\1/p')
           TOOLCHAIN_SHA256=$(echo "$TOOLCHAIN_STRING" | cut -d ' ' -f 1)
 
           echo "TOOLCHAIN_FILE=$TOOLCHAIN_FILE" >> "$GITHUB_ENV"
           echo "TOOLCHAIN_SHA256=$TOOLCHAIN_SHA256" >> "$GITHUB_ENV"
+          echo "TOOLCHAIN_PATH=$TOOLCHAIN_PATH" >> "$GITHUB_ENV"
 
       - name: Cache external toolchain
         if: inputs.build_toolchain == false
@@ -174,7 +199,7 @@ jobs:
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt
         run: |
-          wget -O - https://downloads.cdn.openwrt.org/snapshots/targets/${{ env.TARGET }}/${{ env.SUBTARGET }}/${TOOLCHAIN_FILE}.tar.xz \
+          wget -O - https://downloads.cdn.openwrt.org/${{ env.TOOLCHAIN_PATH }}/targets/${{ env.TARGET }}/${{ env.SUBTARGET }}/${{ env.TOOLCHAIN_FILE }}.tar.xz \
             | tar --xz -xf -
 
       - name: Extract prebuilt tools