fix(dev): Check out correct commit in manual GHA Build & Test workflow (#4954)

Our `Build & Test` GHA workflow can be triggered manually, and when you trigger it, you can either pick the branch to run it on or give it a specific commit to test. The former works fine, but the latter does not - though it picks up the given commit and correctly puts it in the env, it doesn't actually use that value when checking out the commit, instead always relying on the default value. This fixes that by always specifying what value to use.

Author: lobsterkatie

.github/workflows/build.yml

@@ -41,6 +41,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
         # we use a hash of yarn.lock as our cache key, because if it hasn't changed, our dependencies haven't changed,
@@ -68,6 +70,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
       - name: Check dependency cache
@@ -109,6 +113,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
         with:
@@ -139,6 +145,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
       - name: Check dependency cache
@@ -162,6 +170,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
       - name: Check dependency cache
@@ -186,6 +196,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ github.sha }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
       - name: Check dependency cache
@@ -223,6 +235,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
         with:
@@ -256,6 +270,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
         with:
@@ -288,11 +304,12 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
         # TODO: removing `fetch-depth` below seems to have no effect, and the commit which added it had no description,
         # so it's not clear why it's necessary. That said, right now ember tests are xfail, so it's a little hard to
         # tell if it's safe to remove. Once ember tests are fixed, let's try again with it turned off, and if all goes
         # well, we can pull it out.
-        with:
           fetch-depth: 0
       - name: Set up Node
         uses: actions/setup-node@v1
@@ -343,6 +360,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
         with:
@@ -381,6 +400,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
       - name: Check dependency cache
@@ -410,6 +431,8 @@ jobs:
     steps:
       - name: Check out current commit (${ env.HEAD_COMMIT }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
         with:
@@ -445,6 +468,8 @@ jobs:
     steps:
       - name: Check out current commit (${{ github.sha }})
         uses: actions/checkout@v2
+        with:
+          ref: ${{ env.HEAD_COMMIT }}
       - name: Set up Node
         uses: actions/setup-node@v1
         with: