thodg/libgit2

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index c9a407a..360edee 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -16,7 +16,7 @@ jobs:
     - name: Calculate image label
       run: |
         git log -1 azure-pipelines/docker/
-        echo "::set-env name=docker-label::libgit2-$(git log -1 --pretty=format:"%h" azure-pipelines/docker/)"
+        echo "::set-env name=docker-label::libgit2-$(git log -1 --pretty=format:"%h" -- azure-pipelines/docker/)"
     - name: Log in to GitHub Packages
       run: |
         docker login https://docker.pkg.github.com -u ${{github.actor}} -p ${{github.token}}