Fix production deployments (#1066)

## Fixes issue
Prod deploy failed.

## Description of Changes
Pushing into the main branch is now longer required for production
deployments, but the task.py script was hard-coded to fetch the (out of
date) main branch.
After this change, the script will now fetch the given git ref, in the
prod deploy case this is the tag used in the release.

.github/workflows/build_deploy.yml

@@ -74,6 +74,6 @@ jobs:
       - name: backup db
         run: invoke backup ${{ env.env_name }}
       - name: deploy
-        run: invoke deploy ${{ env.env_name }} ${{ github.actor }} ${{ secrets.GITHUB_TOKEN }}
+        run: invoke deploy ${{ env.env_name }} ${{ github.actor }} ${{ secrets.GITHUB_TOKEN }} ${{ github.ref_name }}
       - name: cleanup
         run: invoke cleanup ${{ env.env_name }}

tasks.py

@@ -87,9 +87,9 @@ def get_configs(
     return configs[env]
 
 
-def pull_repository(c: Connection, config: HostConfig):
+def pull_repository(c: Connection, github_ref: str):
     """Pull the code on the repo down to the server."""
-    c.run(f"git fetch origin {config.git_branch}")
+    c.run(f"git fetch origin {github_ref}")
     c.run("git reset --hard FETCH_HEAD")
     c.run("git clean -df")
 
@@ -102,7 +102,7 @@ def migrate(c, config):
     )
 
 
-def deploy_(c: Connection, config: HostConfig):
+def deploy_(c: Connection, config: HostConfig, github_ref: str):
     """Deploy the most recent docker image for the given environment."""
     logging.info("Start new deployment.")
     with c.cd(config.code_dir):
@@ -120,7 +120,7 @@ def deploy_(c: Connection, config: HostConfig):
             echo=True,
         )
         logging.info("Get code changes from repo")
-        pull_repository(c, config)
+        pull_repository(c, github_ref)
         logging.info("Run necessary migrations.")
         migrate(c, config)
         logging.info("Bring docker service back up.")
@@ -136,13 +136,14 @@ def deploy_(c: Connection, config: HostConfig):
         "environment": "'staging' or 'prod' indicating which environment to target",
         "github_user": "GitHub user name to authenticate with",
         "github_token": "token to use together with github_user",
+        "github_ref": "ref of the branch or tag to deploy (e.g. /refs/tag/v1.0.1 or /refs/heads/main)",
     }
 )
-def deploy(c, environment, github_user, github_token):
+def deploy(c, environment, github_user, github_token, github_ref):
     """Deploy the most recent docker image for the given environment."""
     config = get_configs(environment, github_user, github_token)
     connection = config.get_connection()
-    deploy_(connection, config)
+    deploy_(connection, config, github_ref)
 
 
 def backup_(c: Connection, config: HostConfig):