Set branches for Docker build in the CI.yml

When you're building a docker file of a branch
(eg. to test a pull request) then use that branch.

Author: rwest

.github/workflows/CI.yml

@@ -83,4 +83,5 @@ jobs:
           push: ${{ github.ref == 'refs/heads/main' && github.repository == 'ReactionMechanismGenerator/RMG-Py' }}
           tags: reactionmechanismgenerator/rmg:latest
           build-args: |
-            RMS_Branch=for_rmg
+            RMG_Py_Branch=${{ github.head_ref || github.ref_name }}
+            RMG_Database_Branch=${{ env.RMG_DATABASE_BRANCH }}

Dockerfile

@@ -45,7 +45,9 @@ ENV PATH="/miniconda/bin:$PATH"
 SHELL ["/bin/bash", "-c"]
 
 # Add build arguments for RMG-Py, RMG-database, and RMS branches.
-ARG RMG_Py_Branch=docker
+# The defaults are set here, but they can be overridden at build time
+# using the --build-arg option, or in the continous integration CI.yml file.
+ARG RMG_Py_Branch=main
 ARG RMG_Database_Branch=main
 
 # cd